Method and apparatus for transmitting control information

ABSTRACT

A method of receiving uplink control information at a communication apparatus in a wireless communication system configured for Time Division Duplex (TDD) operations and having a plurality of cells is described. A first set of at least one of one or more Physical Downlink Control Channel (PDCCH) signals and one or more Physical Downlink Shared Channel (PDSCH) signals are transmitted within M downlink subframes, where M≧1. A second set of at least one of one or more PDCCH signals and one or more PDSCH signals are transmitted within N downlink subframes, where N≧1. Acknowledgment information is received on an uplink subframe, the acknowledgment information including first acknowledgment information corresponding to the first set and second acknowledgment information corresponding to the second set.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of co-pending U.S. application Ser.No. 13/920,987 filed Jun. 18, 2013, which is a continuation of U.S.application Ser. No. 13/513,053 filed on Aug. 17, 2012 (now U.S. Pat.No. 8,488,549), which is the National Phase of PCT/KR2011/007251 filedon Sep. 30, 2011, which claims priority under 35 U.S.C. 119(e) to U.S.Provisional Application Nos. 61/388,579 filed on Sep. 30, 2010,61/411,460 filed on Nov. 8, 2010, 61/413,950 filed on Nov. 15, 2010,61/414,846 filed on Nov. 17, 2010, 61/417,283 filed on Nov. 26, 2010,61/424,038 filed on Dec. 16, 2010, and 61/448,206 filed on Mar. 2, 2011.The contents of all of these applications are hereby incorporated byreference as fully set forth herein in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wireless communication system, andmore particularly to a method and apparatus for transmitting controlinformation.

2. Discussion of the Related Art

Wireless communication systems have been widely used to provide variouskinds of communication services such as voice or data services.Generally, a wireless communication system is a multiple access systemthat can communicate with multiple users by sharing available systemresources (bandwidth, transmission (Tx) power, and the like). A varietyof multiple access systems can be used. For example, a Code DivisionMultiple Access (CDMA) system, a Frequency Division Multiple Access(FDMA) system, a Time Division Multiple Access (TDMA) system, anOrthogonal Frequency Division Multiple Access (OFDMA) system, a SingleCarrier Frequency-Division Multiple Access (SC-FDMA) system, and thelike.

SUMMARY OF THE INVENTION

An object of the present invention devised to solve the problem lies ina method and apparatus for efficiently transmitting control informationin a wireless communication system. Another object of the presentinvention devised to solve the problem lies in a method and apparatusfor efficiently transmitting uplink control information using aplurality of cells, and efficiently managing resources associated withthe uplink control information. It is to be understood that technicalobjects to be achieved by the present invention are not limited to theaforementioned technical objects and other technical objects which arenot mentioned herein will be apparent from the following description toone of ordinary skill in the art to which the present inventionpertains.

The object of the present invention can be achieved by providing amethod of transmitting uplink control information at a communicationapparatus configured with Time Division Duplex (TDD) and a plurality ofcells in a wireless communication system, the method including receivingat least one of one or more Physical Downlink Control Channel (PDCCH)signals and one or more Physical Downlink Shared Channel (PDSCH) signalson a plurality of downlink subframes and the plurality of cells;generating acknowledgement information per cell in response to the atleast one of one or more PDCCH and one or more PDSCH; and transmitting aplurality of per-cell acknowledgement information on a single uplinksubframe corresponding to the plurality of downlink subframes, theplurality of per-cell acknowledgement information being concatenatedsequentially in order of cell index, wherein if a PDSCH signal without acorresponding PDCCH signal is present among the one or more PDSCHsignals, acknowledgment information in response to the specific PDSCHsignal is placed at an end of acknowledgment information configured fora cell on which the specific PDSCH signal is received.

In another aspect of the present invention, a communication apparatusconfigured to transmit uplink control information in a wirelesscommunication system, wherein the communication apparatus configuredwith Time Division Duplex (TDD) and a plurality of cells includes aRadio Frequency (RF) unit; and a processor, wherein the processor isconfigured to receive at least one of one or more Physical DownlinkControl Channel (PDCCH) signals and one or more Physical Downlink SharedChannel (PDSCH) signals on a plurality of downlink subframes and theplurality of cells, to generate acknowledgement information per cell inresponse to the at least one of one or more PDCCH and one or more PDSCH,and to transmit a plurality of per-cell acknowledgement information on asingle uplink subframe corresponding to the plurality of downlinksubframes, the plurality of per-cell acknowledgement information beingconcatenated sequentially in order of cell index, wherein if a PDSCHsignal without a corresponding PDCCH signal is present among the one ormore PDSCH signals, acknowledgment information in response to thespecific PDSCH signal is placed at an end of acknowledgment informationconfigured for a cell on which the specific PDSCH signal is received.

The specific PDSCH may be received on a Primary Cell (PCell).

If the plurality of per-cell acknowledgement information are transmittedvia a Physical Uplink Shared Channel (PUSCH), a payload size of theper-cell acknowledgement information may be determined using a DownlinkAssignment Index (DAI) value of a PDCCH for PUSCH scheduling.

The DAI value may indicate a number of downlink subframes per cell onwhich the at least one of one or more PDCCH signals and one or morePDSCH signals can be present.

If the plurality of per-cell acknowledgement information are transmittedvia a Physical Uplink Control Channel (PUCCH), a payload size of theper-cell acknowledgement information may be determined using a totalnumber of downlink subframes corresponding to the single uplinksubframe.

The plurality of per-cell acknowledgement information may beconcatenated in increasing order of cell index.

As is apparent from the above description, exemplary embodiments of thepresent invention can provide a method and apparatus for efficientlytransmitting control information in a wireless communication system. Inmore detail, the embodiments of the present invention efficiently cantransmit uplink control information using a plurality of cells, and canefficiently manage resources associated with the uplink controlinformation.

It will be appreciated by persons skilled in the art that the effectsthat can be achieved with the present invention are not limited to whathas been particularly described hereinabove and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention.

FIG. 1 is a conceptual diagram illustrating physical channels used in a3GPP LTE system acting as an exemplary mobile communication system and ageneral method for transmitting a signal using the physical channels.

FIG. 2, including (a) and (b), is a diagram illustrating a structure ofa radio frame.

FIG. 3 exemplarily shows a resource grid of a downlink slot.

FIG. 4 illustrates a downlink frame structure.

FIG. 5 illustrates an uplink subframe structure.

FIG. 6 shows an example for deciding PUCCH resources for ACK/NACK.

FIG. 7 exemplarily shows an uplink semi-persistent scheduling (SPS)operation scheme.

FIG. 8 exemplarily shows a carrier aggregation (CA) communicationsystem.

FIG. 9 exemplarily shows cross-carrier scheduling.

FIGS. 10 and 11 exemplarily show block-spreading based E-PUCCH formats.

FIG. 12 is a flowchart illustrating a process for processing UL-SCH dataand control information.

FIG. 13 is a conceptual diagram illustrating that control informationand UL-SCH data are multiplexed on a Physical Uplink Shared CHannel(PUSCH).

FIGS. 14 to 26 exemplarily show a method for transmitting ACK/NACKaccording to embodiments of the present invention.

FIG. 27 exemplarily shows the problems encountered when ACK/NACK payloadfor SPS PDSCH is configured.

FIGS. 28 to 32 exemplarily show a method for transmitting ACK/NACKaccording to embodiments of the present invention.

FIG. 33 is a block diagram illustrating a Base Station (BS) and a userequipment (UE) applicable to the embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention with reference to the accompanying drawings. Thedetailed description, which will be given below with reference to theaccompanying drawings, is intended to explain exemplary embodiments ofthe present invention, rather than to show the only embodiments that canbe implemented according to the invention. The following embodiments ofthe present invention can be applied to a variety of wireless accesstechnologies, for example, CDMA, FDMA, TDMA, OFDMA, SC-FDMA, MC-FDMA,and the like. CDMA can be implemented by wireless communicationtechnologies, such as Universal Terrestrial Radio Access (UTRA) orCDMA2000. TDMA can be implemented by wireless communicationtechnologies, for example, a Global System for Mobile communications(GSM), a General Packet Radio Service (GPRS), an Enhanced Data rates forGSM Evolution (EDGE), etc. OFDMA can be implemented by wirelesscommunication technologies, for example, IEEE 802.11 (Wi-Fi), IEEE802.16 (WiMAX), IEEE 802.20, E-UTRA (Evolved UTRA), and the like. UTRAis a part of a Universal Mobile Telecommunications System (UMTS). 3rdGeneration Partnership Project (3GPP) Long Term Evolution (LTE) is apart of an Evolved UMTS (E-UMTS) that uses an E-UTRA. The LTE—Advanced(LTE-A) is an evolved version of 3GPP LTE.

Although the following embodiments of the present invention willhereinafter describe inventive technical characteristics on the basis ofthe 3GPP LTE/LTE-A system, it should be noted that the followingembodiments will be disclosed only for illustrative purposes and thescope and spirit of the present invention are not limited thereto.Specific terms used for the exemplary embodiments of the presentinvention are provided to aid in understanding of the present invention.These specific terms may be replaced with other terms within the scopeand spirit of the present invention.

In a wireless communication system, a user equipment (UE) may receiveinformation from a base station (BS) via a downlink, and may transmitinformation via an uplink. The information that is transmitted andreceived to and from the UE includes data and a variety of controlinformation. A variety of physical channels are used according tocategories of transmission (Tx) and reception (Rx) information of theUE.

FIG. 1 is a conceptual diagram illustrating physical channels for use ina 3GPP system and a general method for transmitting a signal using thephysical channels.

Referring to FIG. 1, when powered on or when entering a new cell, a UEperforms initial cell search in step S101. The initial cell searchinvolves synchronization with a BS. Specifically, the UE synchronizeswith the BS and acquires a cell Identifier (ID) and other information byreceiving a Primary Synchronization CHannel (P-SCH) and a SecondarySynchronization CHannel (S-SCH) from the BS. Then the UE may acquireinformation broadcast in the cell by receiving a Physical BroadcastCHannel (PBCH) from the BS. During the initial cell search, the UE maymonitor a downlink channel status by receiving a downlink ReferenceSignal (DL RS).

After initial cell search, the UE may acquire more specific systeminformation by receiving a Physical Downlink Control CHannel (PDCCH) andreceiving a Physical Downlink Shared CHannel (PDSCH) based oninformation of the PDCCH in step S102.

Thereafter, if the UE initially accesses the BS, it may perform randomaccess to the BS in steps S103 to S106. For random access, the UE maytransmit a preamble to the BS on a Physical Random Access CHannel(PRACH) in step S103 and receive a response message for the randomaccess on a PDCCH and a PDSCH corresponding to the PDCCH in step S104.In the case of contention-based random access, the UE may transmit anadditional PRACH in step S105, and receive a PDCCH and a PDSCHcorresponding to the PDCCH in step S106 in such a manner that the UE canperform a contention resolution procedure.

After the above random access procedure, the UE may receive aPDCCH/PDSCH (S107) and transmit a Physical Uplink Shared CHannel(PUSCH)/Physical Uplink Control CHannel (PUCCH) (S108) in a generaluplink/downlink signal transmission procedure. Control information thatthe UE transmits to the BS is referred to as uplink control information(UCI). The UCI includes a Hybrid Automatic Repeat and reQuestACKnowledgment/Negative-ACK (HARQ ACK/NACK) signal, a Scheduling Request(SR), Channel Quality Indictor (CQI), a Precoding Matrix Index (PMI),and a Rank Indicator (RI). In the specification, the HARQ ACK/NACK issimply referred to as a HARQ-ACK or ACK/NACK (A/N). The HARQ-ACKincludes at least one of a positive ACK (simply, ACK), a negative ACK(NACK), DTX and NACK/DTX. The UCI is transmitted on a PUCCH, in general.However, the UCI can be transmitted on a PUSCH when control informationand traffic data need to be transmitted simultaneously. Furthermore, theUCI can be aperiodically transmitted on a PUSCH at therequest/instruction of a network.

FIG. 2, including (a) and (b), illustrates a radio frame structure. In acellular OFDM wireless packet communication system, UL/DL data packettransmission is performed based on subframe. One subframe is defined asa predetermined interval including a plurality of OFDM symbols. 3GPP LTEsupports a type-1 radio frame applicable to Frequency Division Duplex(FDD) and type-2 radio frame applicable to Time Division Duplex (TDD).

FIG. 2( a) illustrates a type-1 radio frame structure. A DL radio frameincludes 10 subframes each having 2 slots in the time domain. A timerequired to transmit one subframe is referred to as Transmission TimeInterval (TTI). For example, one subframe is 1 ms long and one slot is0.5 ms long. One slot includes a plurality of OFDM symbols in the timedomain and a plurality of Resource Blocks (RBs) in the frequency domain.Since 3GPP LTE systems use OFDMA in downlink, an OFDM symbol representsone symbol interval. The OFDM symbol can be called an SC-FDMA symbol orsymbol interval. An RB as a resource allocation unit may include aplurality of consecutive subcarriers in one slot.

The number of OFDM symbols included in one slot may depend on CyclicPrefix (CP) configuration. CPs include an extended CP and a normal CP.When an OFDM symbol is configured with the normal CP, for example, thenumber of OFDM symbols included in one slot may be 7. When an OFDMsymbol is configured with the extended CP, the length of one OFDM symbolincreases, and thus the number of OFDM symbols included in one slot issmaller than that in case of the normal CP. In case of the extended CP,the number of OFDM symbols allocated to one slot may be 6. When channelstate is unstable, such as a case in which a UE moves at a high speed,the extended CP can be used to reduce inter-symbol interference.

When the normal CP is used, one subframe includes 14 OFDM symbols sinceone slot has 7 OFDM symbols. The first three OFDM symbols at most ineach subframe can be allocated to a PDCCH and the remaining OFDM symbolscan be allocated to a PDSCH.

FIG. 2( b) illustrates a type-2 radio frame structure. The type-2 radioframe includes 2 half frames. Each half frame includes 5 subframes, aDownlink Pilot Time Slot (DwPTS), a Guard Period (GP), and an UplinkPilot Time Slot (UpPTS), and one subframe consists of 2 slots. The DwPTSis used for initial cell search, synchronization or channel estimation.The UpPTS is used for channel estimation in a BS and UL transmissionsynchronization acquisition in a UE. The GP eliminates UL interferencecaused by multi-path delay of a DL signal between a UL and a DL.

The aforementioned structure of the radio frame is only exemplary, andvarious modifications can be made to the number of subframes containedin the radio frame or the number of slots contained in each subframe, orthe number of OFDM symbols in each slot.

FIG. 3 exemplarily shows a resource grid of a downlink slot.

Referring to FIG. 3, a downlink slot includes a plurality of OFDMsymbols in a time domain. One downlink slot includes 7 (or 6) OFDMsymbols and a resource block (RB) includes 12 subcarriers in a frequencydomain. Each element on a resource grid may be defined as a resourceelement (RE). One RB includes 12×7 (or 12×6) REs. The number (NRB) ofRBs contained in a downlink slot is dependent upon a downlinktransmission bandwidth. An uplink slot structure is identical to thedownlink slot structure, but OFDM symbols are replaced with SC-FDMAsymbols in the uplink slot structure differently from the downlink slotstructure.

FIG. 4 is a downlink subframe structure.

Referring to FIG. 4, a maximum of three (or four) OFDM symbols locatedin the front part of a first slot of the subframe may correspond to acontrol region to which a control channel is allocated. The remainingOFDM symbols correspond to a data region to which a Physical DownlinkShared CHannel (PDSCH) is allocated. A variety of downlink controlchannels may be used in the LTE, for example, a Physical Control FormatIndicator Channel (PCFICH), a Physical Downlink Control Channel (PDCCH),a Physical hybrid ARQ indicator Channel (PHICH), etc. PCFICH istransmitted from a first OFDM symbol of the subframe, and carriesinformation about the number of OFDM symbols used for transmitting acontrol channel within the subframe. PHICH carries a Hybrid AutomaticRepeat request acknowledgment/negative-acknowledgment (HARQ ACK/NACK)signal as a response to an uplink transmission signal.

Control information transmitted over a PDCCH is referred to as DownlinkControl Information (DCI). A variety of DCI formats are defined, forexample, format 0 for uplink, and formats 1, 1A, 1B, 1C, 1D, 2, 2A, 3,3A, etc. for downlink. DCI format may selectively include a variety ofinformation according to various usages. For example, DCI format mayselectively include a hopping flag, RB allocation, modulation codingscheme (MCS), redundancy version (RV), new data indicator (NDI),transmit power control (TPC), cyclic shift demodulation reference signal(CS DM RS), channel quality information (CQI) request, HARQ processnumber, transmitted precoding matrix indicator (TPMI), precoding matrixindicator (PMI) confirmation, etc.

PDCCH carries a variety of information, for example, transmission formatand resource allocation information of a downlink shared channel(DL-SCH), transmission format and resource allocation information of anuplink shared channel (UL-SCH), paging information transmitted over apaging channel (PCH), system information transmitted over DL-SCH,resource allocation information of an upper-layer control message suchas a random access response transmitted over PDSCH, a set of Tx powercontrol commands of each UE contained in a UE group, a Tx power controlcommand, activation indication information of Voice over IP (VoIP), andthe like. A plurality of PDCCHs may be transmitted within a controlregion. A user equipment (UE) can monitor a plurality of PDCCHs. PDCCHis transmitted as an aggregation of one or more contiguous controlchannel elements (CCEs). CCE is a logical allocation unit that is usedto provide a coding rate based on a radio channel state to a PDCCH. CCEmay correspond to a plurality of resource element groups (REGs). Theformat of PDCCH and the number of PDCCH bits may be determined accordingto the number of CCEs. A base station (BS) decides a PDCCH formataccording to DCI to be sent to the UE, and adds a Cyclic RedundancyCheck (CRC) to control information. The CRC is masked with an identifier(e.g., Radio Network Temporary Identifier (RNTI)) according to a PDCCHowner or a purpose of the PDCCH. For example, provided that the PDCCH isprovided for a specific UE, an identifier of the corresponding UE (e.g.,cell-RNTI (C-RNTI)) may be masked with the CRC. If PDCCH is provided fora paging message, a paging identifier (e.g., paging-RNTI (P-RNTI)) maybe masked with a CRC. If PDCCH is provided for system information (e.g.,system information block (SIC)), system information RNTI (SI-RNTI) maybe masked with CRC. If PDCCH is provided for a random access response,random access-RNTI (RA-RNTI) may be masked with CRC.

FIG. 5 is a diagram showing the structure of an uplink subframe used inLTE.

Referring to FIG. 5, the UL subframe includes a plurality of slots(e.g., 2 slots). Each slot may include different numbers of SC-FDMAsymbols according to CP length. The UL subframe is divided into a dataregion and a control region in a frequency domain. The data regionincludes a PUCCH and transmits a data signal such as a voice signal orthe like. The control region includes a PUSCH, and transmits UplinkControl Information (UCI). PUCCH includes a pair of RBs (hereinafterreferred to as an RB pair) located at both ends of the data region on afrequency axis, and is hopped using a slot as a boundary.

PUCCH may be used to transmit the following control information, i.e.,Scheduling Request (SR), HARQ ACK/NACK, and a Channel Quality Indicator(CQI), and a detailed description thereof will hereinafter be described.

-   -   Scheduling Request (SR): Scheduling request (SR) is used for        requesting UL-SCH resources, and is transmitted using an On-Off        Keying (OOK) scheme.    -   HARQ ACK/NACK: HARQ ACK/NACK is a response signal to an uplink        (UL) data packet on a PDSCH. The HARQ ACK/NACK indicates whether        or not a DL data packet has been successfully received. ACK/NACK        of 1 bit is transmitted as a response to a single DL codeword,        and ACK/NACK of 2 bits is transmitted as a response to two DL        codewords.    -   Channel Quality Indicator (CQI): CQI is feedback information for        a downlink channel. MIMO-associated feedback information        includes a Rank Indicator (RI) and a Precoding Matrix Indicator        (PMI). 20 bits are used per subframe.

The amount of control information (i.e., UCI), that is capable of beingtransmitted in a subframe by the UE, is dependent upon the number ofSC-FDMAs available for UCI transmission. SC-FDMAs available in UCItransmission indicate the remaining SC-FDMA symbols other than SC-FDMAsymbols that are used for Reference Signal (RS) transmission in asubframe. In the case of a subframe in which a Sounding Reference Signal(SRS) is established, the last SC-FDMA symbol of the subframe is alsoexcluded. The Reference Signal (RS) is used for coherent detection of aPUCCH. PUCCH supports 7 formats according to transmission information.

Table 1 shows the mapping relationship between PUCCH format and UCI foruse in LTE.

TABLE 1 PUCCH format Uplink control information (UCI) Format 1Scheduling request (SR) (unmodulated waveform) Format la 1-bit HARQACK/NACK with/without SR Format lb 2-bit HARQ ACK/NACK with/without SRFormat 2 CQI (20 coded bits) Format 2 CQI and 1- or 2-bit HARQ ACK/NACK(20 bits) for extended CP only Format 2a CQI and 1-bit HARQ ACK/NACK(20 + 1 coded bits) Format 2b CQI and 2-bit HARQ ACK/NACK (20 + 1 codedbits)

Table 1 shows the mapping relationship between PUCCH format and UCI foruse in LTE.

Semi-Persistent Scheduling (SPS)

Scheduling dynamically assigns resources to general unicast data on aper subframe basis. In contrast, SPS is a scheme for reserving resourcesin advance with respect to traffic which is periodically generated at amedium/low data request rate, such as Voice over Internet Protocol(VoIP) or streaming. In the SPS, resources are reserved in advance withrespect to specific traffic such that scheduling overhead is reduced andresources are stably assigned.

In the LTE system, in the case of DL/UL SPS, information about asubframe for performing SPS transmission (Tx)/reception (Rx) is obtainedby RRC signaling, and SPS activation (or reactivation) and deactivationare performed through a PDCCH. Subframe information for the SPS includesa subframe interval and a subframe offset. For convenience, a PDCCHindicating SPS activation/deactivation is called an SPS PDCCH. The SPSPDCCH carries RB assignment information for SPS Tx/Rx and Modulation andCoding Scheme (MCS) information. In addition, theCyclic-Redundancy-Check (CRC) of the SPS PDCCH is masked with an SPSRadio Network Temporary Identifier (RNTI) is set to (NDI=0).Accordingly, even when information about a subframe for receiving theSPS by RRC signaling is assigned, the UE does not immediately performthe SPS Tx/Rx. When the UE receives an SPS PDCCH indicating activation(or reactivation), SPS Tx (e.g., PUSCH transmission) or SPS Rx (e.g.,PDSCH reception) is performed in a subframe assigned by RRC signaling.The SPS Tx/Rx is performed within the subframe using the RB assignmentinformation and the MCS information in the SPS PDCCH. Meanwhile, the UEstops the SPS Tx/Rx when receiving a PDCCH indicating deactivation. Whenan SPS PDCCH indicating activation (or reactivation) is received, thestopped SPS Tx/Rx is resumed in the subframe assigned by the RRCsignaling using the RB assignment information and the MCS informationspecified in the SPS PDCCH.

In the case of SPS activation, a DCI field of the SPS PDCCH is set asshown in the following Table 2, a combination of bit fields shown inTable 2 can be used as a virtual CRC.

TABLE 2 DCI format DCI format 0 1/1A DCI format 2/2A/2B TPC command forset to ‘00’ N/A N/A scheduled PUSCH Cyclic shift DM RS set to ‘000’ N/AN/A Modulation and MSB is set to N/A N/A coding scheme and ‘0’redundancy version HARQ process N/A FDD: set to FDD: set to ‘000’ number‘000’ TDD: set to ‘0000’ TDD: set to ‘0000’ Modulation and N/A MSB isset to For the enabled coding scheme ‘0’ transport block: MSB is set to‘0’ Redundancy version N/A set to ‘00’ For the enabled transport block:set to ‘00’

If an error incapable of being checked by CRC has occurred, the virtualCRC is adapted to determine whether the corresponding bit field value isa promised value, such that it can provide additional error detectioncapability. Although an error occurs in DCI assigned to another UE,provided that this UE does not detect the corresponding error andmistakes the error for its own SPS activation, the UE continuously usesthe corresponding resources, such that one error may cause a persistentproblem. Therefore, the virtual CRC can prevent the SPS from beingwrongly detected.

In the case of SPS release, DCI fields of the SPS PDCCH are establishedas shown in the following Table 3, such that DCI field combinations maybe used as virtual CRCs. In case of SPS release, the UE transmitsACK/NACK for SPS release PDCCH.

TABLE 3 DCI format 0 DCI format 1A TPC command for scheduled PUSCH setto ‘00’ N/A Cyclic shift DM RS set to ‘000’ N/A Modulation and codingscheme and set to ‘11111’ N/A redundancy version Resource blockassignment and Set to all ‘1’s N/A hopping resource allocation HARQprocess number N/A FDD: set to ‘000’ TDD: set to ‘0000’ Modulation andcoding scheme N/A set to ‘11111’ Redundancy version N/A set to ‘00’Resource block assignment N/A Set to all ‘1’s

The uplink Semi-Persistent Scheduling (UL SPS) operating scheme willhereinafter be described. A base station (BS) may inform the UE of asubframe (e.g., 20 ms long) in which the SPS operation must be performedthrough higher layer (e.g., RRC) signaling. The BS transmits an SPSPDCCH indicating SPS activation to a UE 120. In this example, the SPSPDCCH includes UL grant information. In this case, specific RB, MCS,etc. specified by the SPS PDCCH are assigned to the UE for uplinktransmission at an interval of 20 ms after the UL grant information isreceived by SPS signaling. Accordingly, the UE may perform uplinktransmission using the RB information and the MCS information specifiedby the SPS PDCCH at an interval of 20 ms. For convenience ofdescription, PUSCH depending on SPS is referred to as SPS PUSCH. The DLSPS operation is performed similarly to the UL SPS operation. In moredetail, after receiving the SPS activation PDCCH having a DL grant, theUE can receive a DL signal (e.g., PDSCH) using RB and MCS specified bySPS PDCCH at intervals of 20 ms. In case of a PDSCH signal transmittedduring SPS operation, a PDCCH corresponding to the PDSCH signal does notexist. For convenience of description, PDSCH depending on SPS willhereinafter be referred to as SPS PDSCH.

FIG. 6 shows an example for deciding PUCCH resources for ACK/NACK. Inthe LTE system, PUCCH resources for ACK/NACK are not pre-allocated toeach UE, and several UEs located in the cell are configured todivisionally use several PUCCH resources at every time point. In moredetail, PUCCH resources used for ACK/NACK transmission of a UE maycorrespond to a PDCCH that carries scheduling information of thecorresponding DL data. The entire region to which a PDCCH is transmittedin each DL subframe is comprised of a plurality of Control ChannelElements (CCEs), and a PDCCH transmitted to the UE is comprised of oneor more CCEs. The UE may transmit ACK/NACK through PUCCH resources(e.g., first CCE) from among CCEs constructing a PDCCH received by theUE.

Referring to FIG. 6, each block in a Downlink Component Carrier (DL CC)represents a CCE and each block in an Uplink Component Carrier (UL CC)indicates a PUCCH resource. Each PUCCH resource index may correspond toa PUCCH resource for an ACK/NACK signal. If information on a PDSCH isdelivered on a PDCCH composed of CCEs #4, #5 and #6, as shown in FIG. 6,a UE transmits an ACK/NACK signal on PUCCH #4 corresponding to CCE #4,the first CCE of the PDCCH. FIG. 6 illustrates a case in which a maximumof M PUCCHs are present in the UL CC when a maximum of N CCEs exist inthe DL CC. Though N may be identical to M (M=M), N may differ from M andCCEs may be mapped to PUCCHs in an overlapped manner.

Specifically, a PUCCH resource index in an LTE system is determined asfollows.

n(1)PUCCH=nCCE+N(1)PUCCH  [Equation 1]

Here, n(1)PUCCH represents a resource index of PUCCH format 1 forACK/NACK/DTX transmission, N(1)PUCCH denotes a signaling value receivedfrom a higher layer, and nCCE denotes the smallest value of CCE indexesused for PDCCH transmission. A cyclic shift (CS), an orthogonalspreading code and a Physical Resource Block (PRB) for PUCCH formats1a/1b are obtained from n(1)PUCCH.

TDD scheme divides the same frequency band into a DL subframe and a ULsubframe within a time domain, and then uses the DL subframe and the ULsubframe. Therefore, in case of a DL/UL asymmetric data trafficsituation, much more DL subframes may be allocated or much more ULsubframes may be allocated. Therefore, according to the TDD scheme, theDL subframe may be mapped to the UL subframe on a one to one basis.Specifically, if the number of DL subframes is larger than the number ofUL subframes, the UE must transmit an ACK/NACK response in response to aplurality of PDSCHs of multiple DL subframes on a single UL subframe.For example, the ratio of a DL subframe to a UL subframe according tothe TDD configuration may be set to M:1. M is the number of DL subframescorresponding to one UL subframe. In this case, the UE must transmit anACK/NACK response on a single UL subframe upon receiving a plurality ofPDSCHs on M DL subframes.

In more detail, the ACK/NACK signal transmitted on a UL subframe (n) maycorrespond not only to PDCCH(s) detected by DL subframe(s) n−k (kεK) butalso to a DL SPS release PDCCH. K is given by UL-DL configuration. Table4 shows K: {k₀, k₁, . . . , k_(M-1)} defined in the legacy LTE TDD.

TABLE 4 UL-DL Subframe n Configuration 0 1 2 3 4 5 6 7 8 9 0 — — 6 — 4 —— 6 — 4 1 — — 7, 6 4 — — — 7, 6 4 — 2 — — 8, 7, 4, 6 — — — — 8, 7, 4, —— 6 3 — — 7, 6, 11 6, 5 5, — — — — — 4 4 — — 12, 8, 7, 11 6, 5, 4, — — —— — — 7 5 — — 13, 12, 9, 8, 7, 5, 4, 11, — — — — — — — 6 6 — — 7 7 5 — —7 7 —

When several PDSCHs are transmitted to one UE in several DL subframes, aBS transmits one PDCCH to each PDSCH. In this case, a UE may transmit anACK/NACK signal in response to a plurality of PDSCHs on a single ULsubframe through PUCCH or PUSCH. The scheme for transmitting oneACK/NACK signal upon receiving several PDSCHs may be largely classifiedinto an ACK/NACK bundling scheme and a PUCCH selection transmissionscheme.

1) ACK/NACK bundling: ACK/NACK bits for a plurality of data units (forexample, PDSCH, SPS release PDCCH, etc.) are coupled to each other by alogical AND operation. For example, if all data units are successfullydecoded, a reception (Rx) node (e.g., UE) transmits an ACK signal. Incontrast, if any one data unit fails decoding (or detecting), the Rxnode may transmit a NACK signal or no signal.

2) PUCCH selection transmission: UE having received multiple PDSCHsreserves multiple PUCCH resources for ACK/NACK transmission. TheACK/NACK response for multiple data units is identified by a combinationof PUCCH resources used for actual ACK/NACK transmission and transmittedACK/NACK content (e.g., bit values).

When a UE transmits an ACK/NACK signal to a BS according to the TDDscheme, the following problems may occur.

-   -   In the case where the UE transmits the ACK/NACK signal to the BS        using the above-mentioned schemes, it may be assumed that some        parts of PDCCHs that have been transmitted from the base station        during a plurality of subframe intervals may not be received by        the UE (i.e., the UE may miss some parts of PDCCHs). In this        case, it is impossible for the UE to recognize whether a PDSCH        corresponding to the missing PDCCH is transmitted to the UE,        resulting in the occurrence of errors in ACK/NACK generation.

In order to solve the above-mentioned errors, the TDD system includes adownlink assignment index (DAI) in a PDCCH. DAI indicates anaccumulative value (i.e., a counting value) of PDCCH(s) corresponding toPDSCH(s) and PDCCH(s) indicating DL SPS release in the range extended toa current subframe within DL subframe(s) n−k (kεK). For example, ifthree DL subframes are mapped to one UL subframe, PDSCHs transmitted in3 DL subframe intervals are sequentially indexed (i.e., sequentiallycounted), and the indexed result is loaded on a PDCCH that schedules aPDSCH. As a result, the UE can recognize whether a PDCCH has beennormally received on the basis of DAI information contained in thePDCCH.

FIG. 7 exemplarily shows ACK/NACK transmission using a DAI. For example,according to the TDD system shown in FIG. 7, one UL subframe is mappedto three DL subframes (i.e., 3 DL subframes:1 UL subframe). Forconvenience of description, it is assumed that the UE transmits anACK/NACK signal using a PUCCH resource corresponding to the lastdetected PDCCH.

The first example of FIG. 7 shows that a UE missed a second PDCCH. Sincea DAI value (DAI=3) of a third PDCCH is different from the number (i.e.,2) of received PDCCHs, the UE recognizes that the second PDCCH has beenmissed. In this case, the UE transmits ACK/NACK information using PUCCHresources corresponding to DAI=3, and an ACK/NACK response to the secondPDCCH may be indicated by NACK (or NACK/DTX). In contrast, if the UE hasmissed the last PDCCH as shown in the second example, the UE is unableto recognize the absence (i.e., missing) of the last PDCCH because a DAIindex of the last received PDCCH is identical to the number of receivedPDCCHs. Therefore, the UE recognizes that only two PDCCHs have beenscheduled during the DL subframe. The UE transmits ACK/NACK informationusing PUCCH resources corresponding to DAI=2, such that the BS canrecognize absence of a PDCCH including DAI=3.

FIG. 8 exemplarily shows a carrier aggregation (CA) communicationsystem. The LTE-A system is designed to use a carrier aggregation orbandwidth aggregation technique using a plurality of UL/DL frequencyblocks so as to use a wider frequency band. Each frequency block istransmitted using a component carrier (CC). The CC may be regarded as acarrier frequency (or center carrier, center frequency) for thefrequency block.

Referring to FIG. 8, a plurality of UL/DL CCs can be aggregated tosupport a wider UL/DL bandwidth. The CCs may be contiguous ornon-contiguous in the frequency domain. Bandwidths of the CCs can beindependently determined Asymmetrical CA in which the number of UL CCsis different from the number of DL CCs can be implemented. For example,when there are two DL CCs and one UL CC, the DL CCs can correspond tothe UL CC in the ratio of 2:1. A DL CC/UL CC link can be fixed orsemi-statically configured in the system. Even if the system bandwidthis configured with N CCs, a frequency band that a specific UE canmonitor/receive can be limited to M (<N) CCs. Various parameters withrespect to CA can be set cell-specifically, UE-group-specifically, orUE-specifically. Control information may be transmitted/received onlythrough a specific CC. This specific CC can be referred to as a PrimaryCC (PCC) (or anchor CC) and other CCs can be referred to as SecondaryCCs (SCCs).

LTE-A uses the concept of a cell so as to manage radio resources. Thecell is defined as a combination of DL resources and UL resources. Here,the UL resources are not an essential part. Accordingly, the cell can beconfigured with DL resources only, or DL resources and UL resources.When CA is supported, the linkage between a carrier frequency (or DL CC)of a DL resource and a carrier frequency (or UL CC) of a UL resource canbe designated by system information. A cell operating at a primaryfrequency (or PCC) can be referred to as a Primary Cell (PCell) and acell operating at a secondary frequency (or SCC) can be referred to as aSecondary Cell (SCell). The PCell is used for a UE to perform an initialconnection establishment procedure or a connection re-establishmentprocedure. The PCell may refer to a cell designated during a handoverprocedure. The SCell can be configured after RRC connection isestablished and used to provide additional radio resources. The PCelland the SCell can be called a serving cell. Accordingly, for a UE thatdoes not support CA while in an RRC_connected state, only one servingcell configured with a PCell exists. Conversely, for a UE that is in anRRC_Connected state and supports CA, one or more serving cells includinga PCell and a SCell are provided. For CA, a network can configure one ormore SCells for a UE that supports CA in addition to a PCell initiallyconfigured during a connection establishment procedure after an initialsecurity activation procedure.

When cross-carrier scheduling (or cross-CC scheduling) is applied, aPDCCH for DL allocation can be transmitted through DL CC#0 and a PDSCHcorresponding thereto can be transmitted through DL CC#2. For cross-CCscheduling, introduction of a Carrier Indicator Field (CIF) may beconsidered. The presence or absence of a CIF in a PDCCH can be setsemi-statically and UE-specifically (or UE-group-specifically) accordingto higher layer signaling (e.g. RRC signaling). The base line of PDCCHtransmission is summarized as follows.

-   -   CIF disabled: PDCCH on a DL CC allocates a PDSCH resource on the        same DL CC or allocates a PUSCH resource on a linked UL CC.    -   CIF enabled: PDCCH on a DL CC can allocate a PDSCH or a PUSCH on        a specific UL/DL CC from among a plurality of aggregated DL/UL        CCs using the CIF.

When a CIF is present, a BS can allocate a PDCCH monitoring DL CC set inorder to reduce BD complexity of a UE. The PDCCH monitoring DL CC setincludes one or more DL CCs as part of aggregated DL CCs, and the UEdetects/decodes a PDCCH only on DL CCs corresponding to the DL CC set.That is, if the BS schedules PDSCH/PUSCH for the UE, the PDCCH istransmitted only through a PDCCH monitoring DL CC set. The PDCCHmonitoring DL CC set can be determined UE-specifically,UE-group-specifically or cell-specifically. The term “PDCCH monitoringDL CC” can be replaced by equivalent terms “monitoring carrier”,“monitoring cell”, etc. In addition, the term “aggregated CC” for a UEcan be replaced by terms “serving CC”, “serving carrier”, “servingcell”, etc.

FIG. 9 illustrates scheduling when a plurality of carriers isaggregated. It is assumed that 3 DL CCs are aggregated and DL CC A isset to a PDCCH monitoring DL CC. DL CC A, DL CC B and DL CC C can becalled serving CCs, serving carriers, serving cells, etc. In case of CIFdisabled, a DL CC can transmit only a PDCCH that schedules a PDSCHcorresponding to the DL CC without a CIF. When the CIF is enabledaccording to UE-specific (or UE-group-specific or cell-specific) higherlayer signaling, DL CC A (monitoring DL CC) can transmit not only aPDCCH that schedules the PDSCH corresponding to the DL CC A but alsoPDCCHs that schedule PDSCHs of other DL CCs. In this case, DL CC B andDL CC C that are not set to a PDCCH monitoring DL CCs do not deliverPDCCHs.

LTE-A considers transmission of a plurality of ACK/NACKinformation/signals with respect to a plurality of PDSCHs, which aretransmitted through a plurality of DL CCs, through a specific UL CC. Toachieve this, it can be considered to joint-code (Reed-Muller code,Tail-biting convolutional code, etc.) a plurality of ACK/NACKs andtransmit a plurality of ACK/NACK information/signals using PUCCH format2, or a new PUCCH format (referred to as an Enhanced PUCCH (E-PUCCH) orPUCCH format M), distinguished from ACK/NACK transmission using PUCCHformat 1a/1b in the legacy LTE system. The E-PUCCH format includes thefollowing block-spreading based PUCCH format. After joint coding,ACK/NACK transmission using E-PUCCH format is exemplary, and E-PUCCHformat may be used without being limited to UCI transmission. Forexample, E-PUCCH format may be used to transmit ACK/NACK, CSI (e.g. CQI,PMI, RI, PTI, etc.), SR, or two or more thereof. Accordingly, E-PUCCHformat may be used to transmit joint-coded UCI codewords irrespective oftype/number/size of UCI.

FIG. 10 illustrates a block-spreading based E-PUCCH format (also called‘PUCCH format M’) at a slot level. In the block-spreading based E-PUCCHformat, one symbol sequence is transmitted over the frequency domain andUE multiplexing is performed using Orthogonal Cover Code (OCC) basedtime-domain spreading. That is, the symbol sequence istime-domain-spread using the OCC and transmitted. Control signals of aplurality of UEs can be multiplexed on the same RB using the OCC.

Referring to FIG. 10, 5 SC-FDMA symbols (i.e., UCI data part) aregenerated from one symbol sequence {d1, d2, . . . } using a length-5(Spreading Factor (SF)=5) OCC (C1, C2, C3, C4, C5). The symbol sequence{d1, d2, . . . } may be a modulation symbol sequence or a codeword bitsequence. When the symbol sequence {d1, d2, . . . } corresponds to thecodeword bit sequence, the block diagram of FIG. 10 further includes amodulation block. In FIG. 10, while 2 RS symbols (i.e., RS) are used inone slot, it is possible to consider various applications including ascheme of using an RS part composed of 3 RS symbols and a UCI data partconfigured using an OCC with SF=4. Here, an RS symbol may be generatedfrom a CAZAC sequence having a specific cyclic shift (CS). An RS may betransmitted in such manner that a specific OCC is applied to (multipliedby) a plurality of RS symbols in the time domain. Block-spread UCI issubjected to Fast Fourier Transform (FFT) and Inverse FFT (IFFT) foreach SC-FDMA symbol and transmitted to a network. That is, theblock-spreading scheme modulates control information using SC-FDMA,distinguished from PUCCH format 1 or 2a/2b of LTE.

FIG. 11 illustrates a block-spreading based E-PUCCH format at asubframes level.

Referring to FIG. 11, in slot 0, symbol sequence {d′0, d′1, . . . ,d′11} is mapped to a subcarrier of one SC-FDMA symbol and mapped to 5SC-FDMA symbols according to block spreading using OCC C1 to C5.Similarly, in slot 1, a symbol sequence {d′12, d′13, . . . , d′23} ismapped to a subcarrier of one SC-FDMA symbol and mapped to 5 SC-FDMAsymbols according to block-spreading using ODD C1 to C5. Here, symbolsequences {d′0, d′1, . . . , d′11} and {d′12, d′13, . . . , d′23} inslots 0 and 1 represent symbol sequence {d1, d2, . . . }, shown in FIG.11, which has been subjected to FFT or FFT/IFFT. When symbol sequence{d′0, d′1, d′11} or {d′12, d′13, . . . , d′23} corresponds to symbolsequence {d1, d2, . . . } which has been subjected to FFT, IFFT isadditionally applied to symbol sequence {d′12, d′13, . . . , d′23} or{d′12, d′13, . . . d′23} in order to generate SC-FDMA symbols. Theentire symbol sequence {d′0, d′1, . . . , d′23} is generated byjoint-coding one or more pieces of UCI, and the first half {d′0, d′1, .. . , d′ 11} is transmitted through slot 0 and the remaining {d′12,d′13, . . . , d′23} is transmitted through slot 1. The OCC may bechanged based on slot and UCI data may be scrambled for each SC-FDMAsymbol.

In the following, a channel-coding based UCI (e.g. a plurality ofACK/NACKs) transmission scheme is referred to as “multi-bit UCI coding”transmission scheme for convenience of description. For example, themulti-bit UCI coding transmission scheme joint-codes PDSCHs of aplurality of DL cells and/or ACK/NACK signals or DTX information(indicating that no PDCCH is received/detected) with respect to PDCCHsthat indicate Semi-Persistent Scheduling (SPS) release to generate acoded ACK/NACK block, and transmits the coded ACK/NACK block. If a UEreceives 2 codewords by operating in a Single User-Multiple InputMultiple Output (SU-MIMO) mode in a DL cell, 4 feedback states ofACK/ACK, ACK/NACK, NACK/ACK, and NCK/NACK, or five feedback statesadditionally including DTX may be present for the cell. If the UEreceives a single codeword, 3 feedback states of ACK, NACK and DTX maybe present (2 feedback states of ACK and NACK/DTX may be present if NACKand DTX are equally processed). Accordingly, when the UE aggregates amaximum of 5 DL cells and operates in the SU-MIMO mode, a maximum of 55feedback states may be present. Therefore, a required ACK/NACK payloadsize is at least 12 bits. If DTX and NACK are equally handled, thenumber of feedback states becomes 45 and the required ACK/NACK payloadsize is at least 10 bits.

M resources for PUCCH format may be explicitly given. In more detail, aPUCCH resource set is configured by a higher layer (e.g., RRC), andPUCCH resources to be actually used may be indicated by an ACK/NACKResource Indicator (ARI) of the PDCCH.

Table 5 explicitly shows PUCCH resources for HARQ-ACK.

TABLE 5 Value of HARQ-ACK resource for PUCCH (ARI) nPUCCH 00 First PUCCHresource value configured by higher layer 01 Second PUCCH resource valueconfigured by higher layer 10 Third PUCCH resource value configured byhigher layer 11 Fourth PUCCH resource value configured by higher layer

ARI represents an ACK/NACK resource indicator. In Table 5, the higherlayer may include an RRC layer and an ARI value may be indicated by aPDCCH carrying a DL grant. For example, the ARI value may be designatedusing an SCell PDCCH and/or a Transmit Power Control (TPC) field of oneor more PCell PDCCHs that do not correspond to a DAI initial value.

LTE-A classifies a method for simultaneously transmitting UCI and UL-SCHdata into a first method for simultaneously transmitting PUCCH and PUSCHand a second method for simultaneously transmitting PUSCH and UCI in thesame manner as in the legacy LTE. Information as to whether simultaneoustransmission of PUCCH and PUSCH is allowed may be established by ahigher layer. If simultaneous transmission of PUCCH and PUSCH isenabled, the first method is used. If simultaneous transmission of PUCCHand PUSCH is disabled, the second method is used.

Since the legacy LTE UE is unable to simultaneously transmit PUCCH andPUSCH, it multiplexes UCI to a PUSCH region when UCI (e.g., CQI/PMI,HARQ-ACK, RI, etc.) transmission is needed for a subframe via whichPUSCH is transmitted. For example, provided that HARQ-ACK transmissionis needed for a subframe to which PUSCH transmission is allocated, theUE multiplexes UL-SCH data and CQI/PMI prior to DFT spreading, and thensimultaneously transmits control information and data over PUSCH.

FIG. 12 is a flowchart illustrating a process for processing UL-SCH dataand control information.

Referring to FIG. 12, error detection is provided to a UL-SCH transportblock (TB) through Cyclic Redundancy Check (CRC) attachment at stepS100.

All the transport blocks (TBs) are used to calculate CRC parity bits.Transport Block (TB) bits are denoted by a₀, a₁, a₂, a₃, . . . ,a_(A-1). Parity bits are denoted by p₀, p₁, p₂, p₃, . . . , p_(L-1). Thesize of TBs is denoted by A, and the number of parity bits is denoted byL.

After performing transport block (TB) CRC attachment, code blocksegmentation and code block CRC attachment are performed at step S110.Input bits for code block segmentation are denoted by b₀, b₁, b₂, b₃, .. . , b_(B-1), where B denotes the number of bits of a TB (includingCRC). Bits provided after code block segmentation are denoted by c_(r0),c_(r1), c_(r2), c_(r3), . . . , c_(r(K) _(r) ₋₁₎, where r denotes a codeblock number (r=0, 1, . . . , C−1) Kr denotes the number of bits of acode block (r), and C denotes a total number of code blocks.

Channel coding is performed after performing the code block segmentationand code block CRC attachment at step S120. Bits after channel codingare denoted by d_(r0) ^((i)), d_(r1) ^((i)), d_(r2) ^((i)), d_(r3)^((i)), . . . , d_(r(D) _(r) ₋₁₎ ^((i)), where i=0, 1, 2. D_(r) is thenumber of bits of an i-th coded stream for the code block (r) (i.e.,D_(r)=K_(r)+4), r denotes a code block number (r=0, 1, . . . , C−1), andKr denotes the number of bits of a code block (r). C denotes a totalnumber of code blocks. Turbo coding may be used for such channel coding.

Rate matching may be performed after channel coding at step S130. Bitsprovided after rate matching are denoted by e_(r0), e_(r1), e_(r2),e_(r3), . . . , e_(r(E) _(r) ₋₁₎. E_(r) is the number of rate-matchedbits of the r-th code block (where r=0, 1, . . . , C−1), and C is atotal number of code blocks.

Code block concatenation is performed after rate matching at step S140.Bits provided after code block concatenation are denoted by f₀, f₁, f₂,f₃, . . . , f_(G-1). G denotes a total number of bits coded for datatransmission. If control information is multiplexed with UL-SCHtransmission, bits used for control information transmission are notincluded in ‘G’. f₀, f₁, f₂, f₃, . . . , f_(G-1) may correspond toUL-SCH codewords.

In the case of UL control information (UCI), channel quality information(CQI and/or PMI), RI and HARQ-ACK are independently channel-coded. UCIchannel coding is performed on the basis of the number of coded symbolsfor each piece of control information. For example, the number of codedsymbols may be used for rate matching of the coded control information.In a subsequent process, the number of coded symbols may correspond tothe number of modulation symbols or the number of REs.

HARQ-ACK channel coding is performed using an input bit sequence [o₀^(ACK)], [o₀ ^(ACK) o₁ ^(ACK)] or [o₀ ^(ACK) o₁ ^(ACK) . . . o_(o)_(ACK) ₋₁ ^(ACK)] at step S170. [o₀ ^(ACK)] and [o₀ ^(ACK) o₁ ^(ACK)]denote 1-bit HARQ-ACK and 2-bit HARQ-ACK, respectively. In addition, [o₀^(ACK) o₁ ^(ACK) . . . o_(o) _(ACK) ₋₁ ^(ACK)] denotes HARQ-ACK composedof two or more bits (i.e., O^(ACK)>2). ACK is coded into 1, and NACK iscoded into 0. In the case of the 1-bit HARQ-ACK, repetition coding isused. In the case of the 2-bit HARQ-ACK, the (3,2) simplex code is used,and the encoded data may be cyclically repeated.

Table 6 exemplarily shows channel coding of the 1-bit HARQ-ACK, andTable 7 exemplarily shows HARQ-ACK channel coding.

Q_(m) Encoded HARQ-ACK 2 [o₀ ^(ACK) y] 4 [o₀ ^(ACK) y x x] 6 [o₀ ^(ACK)y x x x x]

TABLE 7 Q_(m) Encoded HARQ-ACK 2 [o₀ ^(ACK) o₁ ^(ACK) o₂ ^(ACK) o₀^(ACK) o₁ ^(ACK) o₂ ^(ACK)] 4 [o₀ ^(ACK) o₁ ^(ACK) x x o₂ ^(ACK) o₀^(ACK) x x o₁ ^(ACK) o₂ ^(ACK) x x] 6 [o₀ ^(ACK) o₁ ^(ACK) x x x x o₂^(ACK) o₀ ^(ACK) x x x x o₁ ^(ACK) o₂ ^(ACK) x x x x]

In Tables 6 and 7, Qm is a modulation order. For example, Qm=2, Qm=4,and Qm=6 may correspond to QPSK, 16QAM, and 64QAM, respectively. o₀^(ACK) may correspond to an ACK/NACK bit for the codeword 0, and o₁^(ACK) may correspond to an ACK/NACK bit for the codeword 1. o₀ ^(ACK)is denoted by o₂ ^(ACK)=(o₀ ^(ACK)+o₁ ^(ACK)) mod 2, and ‘mod’ is amodulo operation. ‘x’ or ‘y’ is a place holder for maximizing aEuclidean distance of a modulation symbol carrying RI information whenthe HARQ-ACK bit is scrambled. Each of ‘x’ and ‘y’ is set to 0 or 1.

Q_(ACK) is a total number of coded bits. Bit sequence q₀ ^(ACK), q₁^(ACK), q₂ ^(ACK), . . . , q_(Q) _(ACK) ₋₁ ^(ACK) is obtained by acombination of coded HARQ-ACK block(s). In order to set the length ofbit sequence to Q_(ACK) the finally-combined coded HARQ-ACK block may bea part not the entirety (i.e., rate matching). Q_(ACK) is denoted byQ_(ACK)=Q′_(ACK)×Q_(m), Q′_(ACK) is the number of coded symbols forHARQ-ACK, and Q_(m) is a modulation order. Q_(m) is established to beidentical to UL-SCH data.

The inputs of a data and control multiplexing block (also called‘data/control multiplexing block’) are coded UL-SCH bits denoted by f₀,f₁, f₂, f₃, . . . , f_(G-1) and coded CQI/PMI bits denoted by q₀, q₁,q₂, q₃, . . . , q_(Q) _(CQI) ₋₁ at step S180. The outputs of the dataand control multiplexing block are denoted by g ₀, g ₁, g ₂, g ₃, . . ., g _(H′-1). g _(i) is a column vector of the length Q_(m) (where i=0, .. . , H′−1), H′ is denoted by H′=H/Q_(m), and H is denoted byH=(G+Q_(CQI)). H is the total number of coded bits allocated for UL-SCHdata and CQI/PMI data.

The input of a channel interleaver includes output data g ₀, g ₁, g ₂, .. . , g _(H′-1) of the data and control multiplexing block, the encodedrank indicators q ₀ ^(RI), q ₁ ^(RI), q ₂ ^(RI), . . . , q _(Q′) _(RI)₋₁ ^(RI) and coded HARQ-ACK data q ₀ ^(ACK), q ₁ ^(ACK), q ₂ ^(ACK), . .. , q _(Q′) _(ACK) ₋₁ ^(ACK) at step S190. g _(i) is a column vector oflength Q_(m) for CQI/PMI (where i=0, . . . H′−1, and H′ is denoted byH′=H/Q_(m)), and q _(i) ^(ACK) is a column vector of length Q_(m) forACK/NACK (where i=0, . . . Q′_(ACK)−1, and Q′_(ACK)=Q_(ACK)/Q_(m)). q_(i) ^(RI) is a column vector of length Q_(m) for RI (where i=0, . . . ,Q′_(RI)−1, and Q′_(RI)=Q_(RI)/Q_(m)).

The channel interleaver multiplexes control information and UL-SCH datafor PUSCH transmission. In more detail, the channel interleaver includesa process of mapping control information and UL-SCH data to a channelinterleaver matrix corresponding to PUSCH resources.

After execution of channel interleaving, the bit sequence h₀, h₁, h₂, .. . , h_(H+Q) _(RI) ⁻¹ that is read row by row from the channelinterleaver matrix is then output. The read bit sequence is mapped to aresource grid. H″=H′+Q′_(RI) modulation symbols are transmitted througha subframe.

FIG. 13 is a conceptual diagram illustrating that control informationand UL-SCH data are multiplexed on a PUSCH. When transmitting controlinformation in a subframe to which PUSCH transmission is allocated, theUE simultaneously multiplexes control information (UCI) and UL-SCH dataprior to DFT spreading. The control information (UCI) includes at leastone of CQI/PMI, HARQ ACK/NACK and RI. The number of REs used fortransmission of each of CQI/PMI, ACK/NACK and RI is dependent uponModulation and Coding Scheme (MCS) and offset values (Δ_(offset) ^(CQI),Δ_(offset) ^(HARQ-ACK), Δ_(offset) ^(RI)) assigned for PUSCHtransmission. The offset values allow different coding rates accordingto control information, and are semi-statically established by an upperlayer (e.g., RRC) signal. UL-SCH data and control information are notmapped to the same RE. Control information is mapped to be contained intwo slots of the subframe.

Referring to FIG. 13, CQI and/or PMI (CQI/PMI) resources are located atthe beginning part of UL-SCH data resources, are sequentially mapped toall SC-FDMA symbols on one subcarrier, and are finally mapped in thenext subcarrier. CQI/PMI is mapped from left to right within eachsubcarrier (i.e., in the direction of increasing SC-FDMA symbol index).PUSCH data (UL-SCH data) is rate-matched in consideration of the amountof CQI/PMI resources (i.e., the number of encoded symbols). Themodulation order identical to that of UL-SCH data may be used inCQI/PMI. ACK/NACK is inserted into some resources of the SC-FDMA mappedto UL-SCH data through puncturing. ACK/NACK is located close to RS,fills the corresponding SC-FDMA symbol from bottom to top (i.e., in thedirection of increasing subcarrier index) within the SC-FDMA symbol. Incase of a normal CP, the SC-FDMA symbol for ACK/NACK is located atSC-FDMA symbols #2 and #5 in each slot as can be seen from FIG. 13.Irrespective of whether ACK/NACK is actually transmitted in a subframe,the coded RI is located next to the symbol for ACK/NACK.

In LTE, control information (e.g., information about QPSK modulation)may be scheduled in a manner that the control information can betransmitted over PUSCH without UL-SCH data. Control information(CQI/PMI, RI and/or ACK/NACK) is multiplexed before DFT spreading so asto retain low CM (Cubic Metric) single-carrier characteristics.Multiplexing of ACK/NACK, RI and CQI/PMI is similar to that of FIG. 7.The SC-FDMA symbol for ACK/NACK is located next to RS, and resourcesmapped to the CQI may be punctured. The number of REs for ACK/NACK andthe number of REs for RI are dependent upon reference MCS (CQI/PMI MCS)and offset parameter (Δ_(offset) ^(CQI), Δ_(offset) ^(HARQ-ACK), orΔ_(offset) ^(RI)). The reference MCS is calculated on the basis of CQIpayload size and resource allocation. Channel coding and rate matchingto implement control signaling having no UL-SCH data are identical tothose of the other control signaling having UL-SCH data.

A method for efficiently transmitting uplink control information (UCI),preferably, ACK/NACK (also called HARQ-ACK), when multiple CCs (that areequivalent to carrier, carrier resource, frequency resource, cell, andthe like) are aggregated in a TDD system, and a resource allocationmethod for the same will hereinafter be described in detail.

For convenience of description, if CC is set to a non-MIMO mode, it isassumed that a maximum of one transport block (TB) (where TB isequivalent to a codeword) can be transmitted at the subframe k of thecorresponding CC. If CC is set to a MIMO mode, it is assumed that amaximum of m TBs (for example, two TBs or two codewords) can betransmitted at the subframe k of the corresponding CC. Information as towhether CC is set to the MIMO mode can be recognized using atransmission mode established by a higher layer. It is assumed that thenumber of ACK/NACK signals (i.e., ACK/NACK bits or HARQ-ARQ bits) of thecorresponding CC is set to 1 (non-MIMO) or m (MIMO) according to atransmission mode established for the corresponding CC, irrespective ofthe number of actually transmitted TBs (or codewords).

Terms for use in the embodiments of the present invention willhereinafter be described in detail.

-   -   HARQ-ACK: HARQ-ACK indicates a reception response to DL        transmission (e.g., PDSCH or SPS release PDCCH). That is,        HARQ-ACK indicates ACK/NACK/DTX response (simply, ACK/NACK        response). The ACK/NACK/DTX response indicates ACK, NACK, DTX or        NACK/DTX. HARQ-ACK for a specific CC or HARQ-ACK of a specific        CC indicates ACK/NACK response to a DL signal (e.g., PDSCH)        related to the corresponding CC. For example, the DL signal may        be scheduled to the corresponding CC). PDSCH may be replaced        with a transport block (TB) or a codeword.    -   SPS release PDCCH: SPS release PDCCH indicates a PDCCH        indicating SPS release. The UE feeds back ACK/NACK information        related to the SPS release PDCCH through uplink.    -   SPS release PDCCH: Term “SPS release PDCCH” indicates a PDCCH        indicating SPS release. The UE feeds back ACK/NACK information        related to the SPS release PDCCH through uplink.    -   SPS PDSCH: Term “SPS PDSCH” indicates a PDSCH transmitted on        downlink using resources semi-statically established by SPS. SPS        PDSCH does not include a DL grant PDCCH corresponding thereto.        In the embodiments of the present invention, SPS PDSCH may be        interchangeably used with ‘PDSCH w/o PDCCH’.    -   SPS PUSCH: Term “SPS PUSCH” indicates a PUSCH transmitted on        downlink using resources semi-statically established by SPS. SPS        PUSCH does not include a UL grant PDCCH. SPS PUSCH does not        include a UL grant PDCCH corresponding thereto. In the        embodiments of the present invention, SPS PUSCH may be        interchangeably used with PUSCH w/o PDCCH′.    -   PUCCH index: PUCCH index corresponds to a PUCCH resource. For        example, the term “PUCCH index” may indicate a PUCCH resource        index. PUCCH resource index may be mapped to at least one of        orthogonal cover (OC), cyclic shift (CS), and PRB.    -   ACK/NACK Resource Indicator (ARI): ARI is used to indicate a        PUCCH resource. For example, ARI (configured by a higher layer)        may be used to indicate a resource modification value (e.g.,        offset) for a specific PUCCH resource (group). In another        example, ARI may also be used to indicate a specific PUCCH        resource (group) index within a PUCCH resource (group) set        (configured by a higher layer). ARI may be contained in a        Transmit Power Control (TPC) field of a PDCCH corresponding to a        PDSCH on an SCC. PUCCH power control may be carried out through        a TPC field contained in a PDCCH (i.e., PDCCH corresponding to a        PDSCH on a PCC) that schedules a PCC. In addition, ARI may have        an initial value of a downlink assignment index (DAI), and may        be contained in a TPC field of the remaining PDCCHs other than a        PDCCH scheduling a specific cell (e.g., PCell). ARI may be        interchangeably used with a HARQ-ACK resource indication value.    -   Downlink Assignment Index (DAI): DAI may be contained in a DCI        transmitted through a PDCCH. DAI may indicate an order value or        counter value of a PDCCH. In the legacy LTE, DAI may be used for        a TDD operation. For convenience of description, DAI of a DL        grant PDCCH is referred to as DL DAI, and DAI of a UL grant        PDCCH is referred to as UL DAI.    -   Implicit PUCCH resource: Implicit PUCCH resource may indicate a        PUCCH resource/index linked to a minimum CCE index of a PDCCH        scheduling a PDCC (See Equation 1).    -   Explicit PUCCH resource: Explicit PUCCH resource may be        indicated by ARI.    -   PDCCH for scheduling CC: “PDCCH for scheduling” may indicate a        PDCCH for scheduling a PDSCH on the corresponding CC. That is,        “PDCCH for scheduling” may indicate a PDCCH corresponding to a        PDSCH on the corresponding CC.    -   PCC PDCCH: PCC PDCCH may indicate a PDCCH scheduling a PCC. That        is, PCC PDCCH may indicate a PDCCH corresponding to a PDSCH on a        PCC. If it is assumed that cross-carrier scheduling is not        allowed for a PCC, PCC PDCCH is transmitted only on PCC.    -   SCC PDCCH: SCC PDCCH indicates a PDCCH scheduling an SCC. That        is, SCC PDCCH may indicate a PDCCH corresponding to a PDSCH on        SCC. If cross-carrier scheduling is allowed on SCC, SCC PDCCH        may be transmitted on PCC. On the other hand, if cross-carrier        scheduling is not allowed on SCC, SCC PDCCH may be transmitted        only on SCC.    -   Cross-CC scheduling: Cross-CC scheduling indicates operations        for scheduling/transmitting all PDCCHs only through a single        PCC.    -   Non-cross-CC scheduling: Non-cross-CC scheduling indicates        operations for scheduling/transmitting a PDCCH scheduling each        CC through the corresponding CC.

Although LTE-A is designed to allow cross-carrier scheduling for a DLPCC, it is also designed to allow only self-carrier scheduling for a DLSCC. In this case, the PDCCH that schedules a PDSCH on a DL PCC may betransmitted only on a DL PCC. On the other hand, a PDCCH that schedulesa PDSCH on a DL SCC may be transmitted on a DL PCC (cross-carrierscheduling), or may be transmitted only on the corresponding DL SCC(self-carrier scheduling).

Embodiment 1

A first embodiment (Embodiment 1) proposes a method for preventingACK/NACK generation errors encountered when a UE has missed a PDCCHunder carrier aggregation (CA) and FDD situation. In more detail, thefirst embodiment (Embodiment 1) provides a method for preventingACK/NACK generation errors from occurring in a CA FDD system, using aDAI used in the legacy TDD. Embodiment 1 provides the following DAIconfiguration methods.

Method 1) Method 1 for indicating a total number of PDCCHs (orcorresponding PDSCHs) transmitted to the corresponding UE through eachPDCCH

FIG. 14 exemplarily shows a method for transmitting ACK/NACK signalsaccording to embodiments of the present invention.

Referring to FIG. 14, a base station (BS) may indicate a UE of a totalnumber of PDCCHs that must be received by the corresponding UE over eachPDCCH when one or more PDCCHs are transmitted to the UE on a single DLsubframe (SF). Information about a total number of PDCCHs may beindicated by a DAI of a PDCCH. In this case, PDCCH may mean a PDCCH(i.e., DL grant PDCCH) for scheduling a PDSCH. For convenience ofdescription, unless mentioned otherwise, PDCCH may mean a DL grantPDCCH. Therefore, the number of PDCCHs may be identical to the number ofPDSCHs.

For example, provided that a BS transmits three PDCCHs to one UE withinone DL subframe, the BS includes information of three PDCCH transmissiononto all of three PDCCHs transmitted to the corresponding UE, andtransmits the resultant PDCCHs. Therefore, if the UE has missed at leastone PDCCH transmitted thereto, the UE can recognize PDCCH missing frominformation about the number of PDCCH(s) in another received PDCCH(s).In more detail, if the UE detects only two PDCCHs, the UE can recognizethat the BS has transmitted three PDCCHs and the UE has received twoPDCCHs.

However, the UE according to the present invention is unable torecognize which one of PDCCHs was missed by the UE. If ACK/NACK istransmitted through each PUCCH resource corresponding to each PDCCH, theBS can recognize a PDCCH missed by the UE because ACK/NACK is nottransmitted on a PUCCH corresponding to the missed PDCCH. However,provided that ACK/NACK is transmitted only through one PUCCH resource,if the PUCCH resource is mapped to a PDCCH order or if the ACK/NACKposition is mapped to the PDCCH order within the ACK/NACK payload, theUE is unable to recognize the order of missed PDCCH such that an errormay occur in PUCCH resource allocation or ACK/NACK payloadconfiguration. Similarly, assuming that ACK/NACK is transmitted througha PUSCH resource and the position of ACK/NACK within the ACK/NACKpayload is mapped to the PDCCH order, errors may also occur in ACK/NACKpayload configuration. Accordingly, the UE is unable to configureACK/NACK resource mapping in case of a PDCCH detection failure. Here,ACK/NACK resource mapping (simply, resource mapping) may include anoperation for mapping each ACK/NACK to a physical resource or ACK/NACKpayload.

Therefore, for the present invention a method (Non-adaptive ACK/NACKtransmission) for enabling a UE to reserve ACK/NACK resourcescorresponding to the number of PDSCHs capable of being maximallyscheduled by a BS at a specific time, so as to cope with a PDCCHdetection failure, may be considered. In this case, each ACK/NACK may bemapped within a physical resource or ACK/NACK payload in the order ofCCs at which the corresponding PDSCH is located.

Method 2) Method for indicating the order value of PDCCH (or thecounterpart PDSCH) transmitted to UE through each PDCCH

FIG. 15 exemplarily shows an ACK/NACK transmission process according toembodiments of the present invention.

Referring to FIG. 15, provided that a BS transmits one or more PDCCHs toa UE within one subframe, the BS may inform the UE of the order value ofeach PDCCH transmitted within the corresponding subframe. The PDCCHorder value may be indicated by a DAI of a PDCCH. For example, providedthat the BS transmits 3 PDCCHs to the UE within one subframe, the BS mayindicate the value of 0, 1 or 2 (or 1, 2 or 3) through each PDCCH. ThePDCCH order may be determined according to a CCE index, the frequencyorder of CC through which a PDSCH is transmitted, or the order ofcarrier indication field (CIF) values of CC.

According to the embodiments of the present invention, provided that aPDCCH having the order value of 0 and a PDCCH having the order value of2 are detected, the UE can recognize not only the missing of PDCCHhaving the order value of 1 but also the missing of PDSCH correspondingto the PDCCH. In other words, differently from Method 1, the UE canrecognize the order of detected PDCCH and the index of missed PDCCH.

However, provided that the UE has missed the last PDCCH, the ordervalues of received PDCCHs are arranged in the order of 0 and 1, suchthat the UE is unable to recognize the missing of last PDCCH. That is,provided that the UE has missed the last contiguous PDCCH(s), the UE isunable to recognize how many PDCCHs are transmitted by the BS. In orderto overcome the above-mentioned problem, the UE can transmit (bundled)ACK/NACK through a PUCCH resource corresponding to a CCE through whichthe last PDCCH is transmitted. For example, if the BS has allocatedthree PDCCHs to the UE and the UE has missed the last PDCCH, the UEtransmits ACK/NACK information through a PUCCH corresponding to a secondPDCCH. Since ACK information is transmitted through the PUCCHcorresponding to the second PDCCH, instead of a PUCCH corresponding tothe last PDCCH, the BS can recognize the absence of the last PDCCH.

In accordance with the present invention, the UE does not recognize atotal number of transmitted PDSCHs (or a total number of PDCCHs forPDSCH scheduling), such that ACK/NACK resources may be preferablyreserved according to the number of PDSCHs capable of being maximallyscheduled. For example, as shown in the drawing, if a maximum of 4PDSCHs can be scheduled, the UE can reserve/transmit ACK/NACK resourceson the assumption that four PDSCHs are always transmitted (Non-adaptiveACK/NACK transmission).

Method 3) Method for indicating the order value of PDCCH (or thecounterpart PDSCH) transmitted to UE and a total number of PDCCHs (orthe counterpart PDSCHs) through each PDCCH

The DAI transmission methods according to Method 1 and Method 2 musttransmit ACK/NACK information in consideration of not only ACK/NACKinformation as to the actually scheduled PDSCH but also all the PDSCHscapable of being scheduled at the corresponding time. Therefore, inorder to be robust against PDCCH detection failure error and to transmitACK/NACK of actually scheduled PDSCH, the UE can be informed of not onlya total number of PDCCHs (or corresponding PDSCHs) transmitted to one UEduring a specific time interval but also the order value of each PDCCH(or each PDSCH), through each PDCCH. The order value of PDCCH and atotal number of PDCCHs may be indicated through a DAI of PDCCH.According to the present invention, it may be possible to transmit onlyACK/NACK of the actually transmitted PDCCH/PDSCH. In addition, in casethat a PDCCH requiring acknowledgement of PDCCH detection exists, atotal sum of PDCCHs (i.e., all PDCCHs causing a UL ACK/NACK response)and the order value of the corresponding PDCCH may be contained in a DAIof the corresponding PDCCH. A representative example of a PDCCHrequiring acknowledgement of PDCCH detection is a PDCCH (i.e., SPSrelease PDCCH) indicating SPS release.

Here, a specific time interval may be a DL subframe corresponding to aUL subframe to which ACK/NACK is to be transmitted. For example, in caseof the FDD system in which a DL subframe is mapped to a UL subframe on aone to one basis, the specific time interval may be one DL subframe. Incase of the TDD system, the specific time interval may be a plurality ofDL subframes.

Preferably, under an assumption that same number of PDCCH transmissionsas a total sum of received PDCCHs, the UE can transmit ACK/NACKinformation (in case of a PDCCH requiring an ACK/NACK response to PDCCHdetection, ACK/NACK information as to PDCCH reception) of PDSCH(s)scheduled by the corresponding PDCCH(s).

FIG. 16 exemplarily shows the ACK/NACK transmission process according tothe present invention. In FIG. 16, provided that a maximum of 4 PDSCHscan be scheduled, the BS transmits a total of 3 PDCCHs and schedules atotal of 3 PDSCHs, and the UE misses the last PDCCH.

Referring to FIG. 16, the UE can recognize a total sum of PDCCHs, suchthat it can recognize the absence of one PDCCH and non-reception of theorder value of 3. As a result, the UE can recognize that the missedPDCCH is the last PDCCH. The UE may determine the ACK/NACK payload sizein consideration of not only a total number of PDCCHs (or a total numberof corresponding PDSCHs) but also a transmission mode of thecorresponding CC, and may configure the ACK/NACK payload inconsideration of the missed PDCCH. For example, the transmission modemay be a single transport block transmission mode (i.e., non-MIMO mode)or multiple-transport blocks transmission mode (i.e., MIMO mode), andmay configure the ACK/NACK payload in consideration of the missed PDCCH.If the CC is in a non-MIMO mode, 1-bit ACK/NACK information may begenerated. If the CC is in a MIMO mode, 2-bit ACK/NACK information maybe generated.

For convenience of description, as shown in Method 1 and Method 2, amethod for transmitting ACK/NACK information as to all PDSCHs (PDCCHsrequiring an ACK/NACK response to PDCCH reception) capable of beingscheduled is referred to as non-adaptive ACK/NACK transmission. In caseof non-adaptive ACK/NACK transmission, it may be necessary to utilizeunnecessary resources during ACK/NACK transmission, and it is impossibleto efficiently reduce a code rate due to an increase of unnecessaryACK/NACK information bits. In contrast, as shown in Method 3, a methodfor adaptively transmitting the number of ACK/NACK signals using correctinformation or upper limit information as to the number of scheduledPDSCHs (and PDCCHs requiring an ACK/NACK response to PDCCH reception) isreferred to as adaptive ACK/NACK transmission. In this case, the numberof scheduled PDCCHs may be equivalent to the number of DL subframesrequiring ACK/NACK feedback.

Information as to which one of non-adaptive ACK/NACK transmission andadaptive ACK/NACK transmission is to be used can be dynamicallydetermined according to whether the UE can use information of the numberof scheduled PDSCHs (and PDCCHs requiring an ACK/NACK response to PDCCHreception). For example, it is assumed that information as to the numberof scheduled PDSCHs (and PDCCHs requiring an ACK/NACK response to PDCCHreception) is transmitted through a PDCCH (i.e., a UL grant PDCCH (e.g.,via a DL DAI field)) scheduling a PUSCH. In this case, assuming thatACK/NACK is transmitted through a PUCCH or a PUSCH w/o PDCCH (e.g., SPSPUSCH), non-adaptive ACK/NACK transmission may be utilized. In otherwords, provided that ACK/NACK is transmitted over a PUSCH with a PDCCH,adaptive ACK/NACK transmission may be utilized.

Embodiment 2

The following two schemes may be used for ACK/NACK transmission.

-   -   Full ACK/NACK scheme: The full ACK/NACK scheme can transmit a        plurality of ACK/NACK signals corresponding to a maximum number        of codewords (CWs) capable of being transmitted through all CCs        assigned to the UE and a plurality of DL subframes (i.e., SF n−k        (kεK)).    -   Bundled ACK/NACK scheme: The bundled ACK/NACK scheme can reduce        the number of all transmission ACK/NACK bits using at least one        of CW bundling, CC bundling, and subframe (SF) bundling and        transmit the ACK/NACK bits.

The CW bundling may applies ACK/NACK bundling to each CC for each DL SF.The CC bundling applies ACK/NACK bundling to all or some of CCs for eachDL SF. SF bundling applies ACK/NACK bundling to all or some of DL SFsfor each CC. ACK/NACK bundling means a logical AND operation performedon a plurality of ACK/NACK responses.

In the case of SF bundling, it is possible to additionally consider“ACK-counter” scheme that indicates the number of ACKs (or the number ofsome of the ACKs) for each CC for all PDSCHs or DL grant PDCCHs receivedfor each CC through ACK/NACK bundling.

If a PUSCH is present at the ACK/NACK transmission time point of thelegacy LTE, the legacy LTE punctures (and/or rate-matches) UL-SCH datapayload, and multiplexes ACK/NACK information with UL-SCH data, suchthat it transmits the multiplexed result over a PUSCH instead of a PUCCH(i.e., ACK/NACK piggyback).

If a PUSCH is present at the ACK/NACK transmission time point of the CAbased FDD system, and if it is impossible to simultaneously transmit aPUSCH and a PUCCH, a method for piggybacking either a bundled ACK/NACK(e.g., a method for indicating the CW bundling or the number of receivedACK signals) or only ACK/NACK of a specific CC on a PUSCH, andtransmitting the piggybacked result may be used to reduce puncturingloss of PUSCH data. In addition, if a PUSCH exists in the ACK/NACKtransmission time point of the CA based FDD system, and if a PUSCH and aPUCCH can be simultaneously transmitted in the CA based FDD system, amethod for transmitting ACK/NACK information over a PUCCH, and at thesame time piggybacking a full or bundled ACK/NACK (e.g., a method forindicating the CW bundling or the number of received ACK signals) oronly ACK/NACK information of a specific CC (e.g., PCC) on a PUSCH may beused to increase the reliability of ACK/NACK transmission. If ACK/NACKis piggybacked on a PUSCH, ACK/NACK bundling (e.g., CW bundling) may bemandatorily used. Alternatively, information as to whether ACK/NACKbundling (e.g., CW bundling) is applied during the ACK/NACK piggybackmay be established through RRC or L1/L2 signaling.

In case of the CA based LTE-A TDD system, multiple ACK/NACK informationpieces/signals of multiple PDSCHs on multiple DL subframes and severalCCs may be transmitted through a specific CC (i.e., primary CC) at a ULsubframe corresponding to the corresponding multiple DL subframes. TheCA based LTE-A TDD system may piggyback full or bundled ACK/NACK on aPUSCH when a PUSCH exists in the ACK/NACK transmission time, andtransmit the piggybacked result. In this case, if the full or bundledACK/NACK payload is increased in size due to many CCs, many CWs and/ormany DL SFs, ACK/NACK bits or symbols piggybacked on a PUSCH areincreased in number, such that there may be a high possibility ofcausing the loss of UL-SCH data throughput.

Therefore, the present invention provides a method for allowing a UE toefficiently transmit ACK/NACK information in the CA based TDD system. Inmore detail, in order to adaptively reduce/decide the size of ACK/NACKpayload piggybacked on a PUSCH in the CA based TDD system, the presentinvention provides a method for indicating ACK/NACK payload informationto be piggybacked on a PUSCH through a PDCCH (i.e., UL grant PDCCH)scheduling a PUSCH. The following Method 1 and Method 2 may be used inthe present invention.

Method 1) Method 1 can indicate the first or last DL SF index in whichat least one PDSCH (or DL grant PDCCH) is scheduled/transmitted for allthe DL CCs.

Method 2) Method 2 can indicate the first or last DL CC index in whichat least one PDSCH (or DL grant PDCCH) is scheduled/transmitted for allthe DL SFs.

Method 3) Method 3 can indicate the first or last ACK/NACK group inwhich at least one PDSCH (or DL grant PDCCH) is scheduled/transmitted.The ACK/NACK group may correspond to a DL CC group, a DL SF group or acombination thereof.

Method 4) Method 4 can indicate an ACK/NACK group to be used forACK/NACK payload configuration. The ACK/NACK group may correspond to aDL CC group, a DL SF group or a combination thereof.

In the present invention, PDSCH or DL grant PDCCH may include PDSCH orPDCCH requiring ACK/NACK response, and may further include a PDCCH thatindicates SPS release.

If ACK/NACK is piggybacked on a PUSCH in the CA based TDD system(irrespective of the presence or absence of CW bundling during PUCCHACK/NACK transmission), CW bundling may be mandatorily applied.Alternatively, information as to whether CW bundling is applied duringACK/NACK piggyback may be established through RRC or L1/L2 signaling. Inmore detail, two states indicating whether CW bundling is applied duringACK/NACK piggyback, and/or one state indicating the absence of ACK/NACKto be piggybacked can be indicated using a DAI field (e.g., 2 bits)contained in the UL grant PDCCH. The above-mentioned method willhereinafter be referred to as Method 0.

Method 1) First or Last PDSCH (PDCCH)—Scheduled DL SF Indication

Method 1 can inform a UE of the first DL SF index (F-SF index) or thelast DL SF index (L-SF index) in which at least one PDSCH (or DL grantPDCCH) is scheduled/transmitted for a DL SF group corresponding to a ULSF, on the basis of a DL SF index. F-SF index or L-SF index indicationinformation may be indicated through a PDCCH scheduling a PUSCH on thecorresponding UL SF. In this case, a PDSCH (e.g., SPS PDSCH) transmittedwithout using a PDCCH is used as the scheduling information known toboth the BS and the UE, such that the corresponding schedulinginformation may be excluded from a PDSCH that decides F-SF or L-SFindex. In more detail, when indicating the F-SF index, ACK/NACK payloadcan be configured only for DL subframes ranging from the F-SF index tothe last SF index. Similarly, when indicating the L-SF index, ACK/NACKpayload can be configured for DL subframes ranging from the first SFindex to the L-SF index.

In addition, DL SF index information may be transmitted through a DAIfield contained in a UL grant PDCCH. The UL grant PDCCH may include“no-PDSCH-state” indication information that indicates the absence ofPDSCH (or DL grant PDCCH) scheduling/transmission in the entire DL SFgroup corresponding to a UL SF. The “no-PDSCH-state” indicationinformation may be transmitted through the DAI field of the UL grantPDCCH. In this case, DL SF index information and “no-PDSCH-state”indication information may be distinguished from each other by differentbits of the DAI field or different DAI states, or may share a specificDAI state. Specifically, if F-SF and L-SF from among several DL SFindexes are present, DL SF having the lowest/highest index from amongthe corresponding DL SF indexes may be indicated by F/L-SF index.

FIG. 17 exemplarily shows the ACK/NACK transmission process according tothe present invention. FIG. 17 assumes a TDD system in which 4 CCs areaggregated and the ratio of DL SF and UL SF is denoted by “DL SF:ULSF=4:1”. Referring to FIG. 17, L-SF in which at least one PDSCH isscheduled/transmitted is transmitted to a UE through a UL grant PDCCH.In this example, L-SF index may indicate DL SF #2. Specifically,considering a 2-bit DAI to indicate the L-SF index, “L-SF index=DL SF#4” may be indicated on the condition that DL SF #3 or #4 is L-SF.

In accordance with another scheme, a method for indicating each DL SFindex in which at least one PDSCH (or DL grant PDCCH) isscheduled/transmitted, in the form of a bitmap may be used.

Meanwhile, the present invention may further provide a method forinforming a UE of a DAI-counter for each DL CC using the DAI fieldcontained in the DL grant PDCCH in a similar way to the legacy LTE TDD.

DAI-Counter (i.e., DL DAI):

DAI-counter (DL DAI) may indicate the order of a PDSCH or DL grant PDCCHscheduled on the basis of the order of DL SF. That is, the DAI-countervalue may indicate an accumulative value (i.e., a counting value) ofPDCCH(s) corresponding to PDSCH(s) and PDCCH(s) indicating DL SPSrelease in the range extended to a current subframe within DLsubframe(s) n−k (kεK) Meanwhile, the order indicated by the DAI-countermay be excluded from a PDSCH (e.g., SPS PDSCH) transmitted without usinga PDCCH. The DAI-counter value may start from 0 or 1, or may start froman arbitrary number. For convenience of description, it is assumed thatthe DAI-counter value starts from 0. For example, if a PDSCH isscheduled through DL SF #1 and DL SF #3, the DAI-counter value containedin a PDCCH that schedules the corresponding PDSCH may be signaled by 0and 1 (or 1 and 2). In case of the 2-bit DAI-counter, the modulo 4operation may be applied to the DAI-counter value of more than 3.

Simultaneously, a maximum value (i.e., maxPDCCHperCC) (that isequivalent to the number of DL subframes requiring ACK/NACK feedback)from among a PDSCH (or a PDCCH, preferably including a PDCCH indicatingSPS release) scheduled/transmitted per DL CC can be indicated through aPDCCH scheduling a PUSCH. The above-mentioned method is referred to asMethod 1-A. In accordance with the present invention, if ACK/NACK istransmitted through a PUCCH or SPS PUSCH, the corresponding PDCCH doesnot exist so that it is impossible to inform the UE of ‘maxPDCCHperCC’information. In this case, ‘maxPDCCHperCC’ may be set to M. M is a totalnumber of DL subframes corresponding to UL subframes to which ACK/NACKis transmitted. M may be defined as shown in Table 4 according to UL-DLconfiguration.

Preferably, PDSCH w/o PDCCH (for example, SPS PDSCH) indicatesscheduling information known to both the BS and the UE, such that SPSPDSCH may be excluded from objective information as necessary. Morepreferably, considering an exemplary case in which only a DL DAI fieldof the PDCCH scheduling a PCC is used for other usages (e.g., the DL DAIfield of the PDCCH is adapted to indicate/move ACK/NACK resources) butnot the DAI-counter, a maximum value from among numbers of per-CCscheduled/transmitted PDSCHs in association with only a DL CC other thana PCC may be indicated by a PDCCH scheduling a PUSCH.

In more detail, the UE may configure per-cell ACK/NACK payload inassociation with PDSCHs (or PDCCHs) corresponding to the range from aDAI-counter initial value to ‘maxPDCCHperCC−1’ (where the DAI-counterstarts from ‘0’) or maxPDCCHperCC′ (where the DAI-counter starts from‘1’). Individual ACK/NACKs may be sequentially located in per-CCACK/NACK payload according to the DAI-counter value of the correspondingPDCCH. Each bit that does not include the corresponding DAI-countervalue in the ACK/NACK payload may be set to a value of NACK, DTX orNACK/DTX. Per-CC ACK/NACK payload may be sequentially concatenatedaccording to CC indexes, such that it may be composed of the entireACK/NACK payload.

Preferably, in order to prevent inconsistency in numbers/positions ofACK/NACK bits between the UE and the BS, the ACK/NACK bits forconstructing per-CC ACK/NACK payload may be determined depending on notonly a transmission mode (i.e., a maximum number of CWs capable of beingtransmitted) per DL CC but also the presence or absence of CW bundlingper DL CC. For example, if a transmission mode established in a CCsupports transmission of a single transport block (TB) or employsbundling, the number of ACK/NACK bits for the corresponding CC may begiven as “2×{the number of subframes (or PDSCHs) where the UE mustperform ACK/NACK feedback}”. In contrast, provided that a transmissionmode established in a CC supports transmission of two TBs and does notemploy bundling, the number of ACK/NACK bits for the corresponding CCmay be given as the number of subframes (or PDSCHs) where the UE mustperform ACK/NACK feedback.

‘maxPDCCHperCC’ information may be transmitted through a DAI field(i.e., UL DAI) contained in a UL grant PDCCH. Considering the use of2-bit DAI, the modulo 4 operation may be applied to ‘maxPDCCHperCC’value of more than ‘3’.

In brief, the entire ACK/NACK payload size can be adjusted using the ULDAI value. In more detail, the size of per-CC ACK/NACK payload (alsocalled ‘ACK/NACK part’) for each DL CC can be determined considering aUL DAI value, a transmission mode of the corresponding CC, and thepresence or absence of bundling. In addition, the position of eachACK/NACK in per-CC ACK/NACK payload can be determined using DL DAIvalue(s) received at each DL CC.

In more detail, it is assumed that the HARQ-ACK feedback bit for thec-th DL CC (or serving cell) is defined as

o_(c, 0)^(ACK)o_(c, 1)^(ACK), …  , o_(c, O_(c)^(ACK) − 1)^(ACK)

(where c≧0). O_(c) ^(ACK) is the number (i.e., size) of HARQ-ACK payloadbits for the c-th DL CC. If a transmission mode for supporting singletransmission block (TB) transmission is established in the c-th DL CC orif the spatial bundling is applied to the c-th DL CC, O_(c) ^(ACK) maybe identical to B_(c) ^(DL) as denoted by O_(c) ^(ACK)=B_(c) ^(DL). Incontrast, if a transmission mode for supporting transmission of multipletransmission blocks (e.g., two TBs) is established in the c-th DL CC orif no spatial bundling is applied to the c-th DL CC, O_(c) ^(ACK) may beidentical to 2B_(c) ^(DL) as denoted by O_(c) ^(ACK)=2B_(c) ^(DL). B_(c)^(DL) is the number (i.e., maxPDCCHperCC) of DL subframes requiringACK/NACK feedback in the c-th DL CC. If HARQ-ACK is transmitted through‘PUSCH w/ PDCCH’, maxPDCCHperCC may be indicated by the value of aUL-DAI field. In contrast, if HARQ-ACK is transmitted through a PUCCH orPUSCH w/o PDCCH, maxPDCCHperCC is denoted by M (i.e., mxPDCCHperCC=M).

If a transmission mode for supporting transmission of a singletransmission block is established in the c-th DL CC, or if spatialbundling is applied to the c-th DL CC, the position of each ACK/NACK inper-CC HARQ-ACK payload is given as o_(c,DAI(k)-1) ^(ACK) DAI(k)indicates a DL DAI value of the PDCCH detected at the DL subframe (n−k).In contrast, if a transmission mode for supporting transmission ofmultiple transmission blocks (e.g., two transmission blocks) isestablished in the c-th DL CC and no spatial bundling is applied to thec-th DL CC, the position of each ACK/NACK in per-CC HARQ-ACK payload isdenoted by o_(c,2DAI(k)-2) ^(ACK) and o_(c,2DAI(k)-1) ^(ACK).o_(c,2DAI(k)-2) ^(ACK) is a HARQ-ACK for the codeword 0, ando_(c,2DAI(k)-1) ^(ACK) is a HARQ-ACK for the codeword 1.

FIG. 18 exemplarily shows the ACK/NACK transmission process according tothe present invention. FIG. 18 assumes a TDD system in which 4 CCs areaggregated and the ratio of DL SF and UL SF is denoted by “DL SF:ULSF=4:1”, and ‘maxPDCCHperCC’ is indicated under a TDD situation.Referring to FIG. 18, the number of PDSCHs scheduled/transmitted for DLCC #1, #2, or #3, or #4 is 2, 3, 1, or 0, respectively. A maximum value(i.e., maxPDCCHperCC=3) from among these values may be indicated by a ULgrant PDCCH. The UE may configure ACK/NACK payload not only for a PDSCHranging from an initial value for each DL CC to a DAI-counter value(i.e., DAI-c) corresponding to (maxPDCCHperCC−1=2), but also forassociated ACK/NACK positions. In this case, the ACK/NACK positionincluding no DAI-counter value may be NACK- or DTX-processed as shown inFIG. 18. For example, if a PDCCH including the corresponding DAI-countervalue is not received, or if maxPDCCHperCC is higher than a maximumvalue of the DAI-counter, the ACK/NACK position information can be NACK-or DTX-processed.

In Method 1-A, if ‘maxPDCCHperCC’ is determined without using ‘PDSCH w/oPDCCH’ (e.g., SPS PDSCH), the ACK/NACK payload size can be more reducedthan the other ACK/NACK payload size obtained when ‘maxPDCCHperCC’ isdetermined in consideration of ‘SPS PDSCH’. In more detail, the UE mayconfigure ACK/NACK payload not only for a PDSCH (or PDCCH) ranging froman initial value for each DL CC to a DAI-counter value (i.e., DAI-c)corresponding to ‘maxPDCCHperCC−1’ (where the DAI-counter starts from 0)or ‘maxPDCCHperCC’ (where the DAI-counter starts from 1), but also forassociated ACK/NACK positions. If PDSCH w/o PDCCH (for example, SPSPDSCH) exists, ACK/NACK bits for SPS PDSCH may be further applied to theACK/NACK payload.

According to the above-mentioned scheme, the size of ACK/NACK payload(i.e. the number (O_(HARQ-ACK)) of ACK/NACK bits) can be represented bythe following equation 2.

$\begin{matrix}{O_{{HARQ} - {ACK}} = {\max \; {{PDCCHperCC} \cdot {\sum\limits_{c = 0}^{C - 1}\; {{TB}_{\max}(c)}}}}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

In Equation 2, ‘maxPDCCHperCC’ is the number of DL subframes (orPDSCHs/PDCCHs) that require ACK/NACK feedback for each CC, C is thenumber of CCs, and TB_(max) (C) is the number of TBs (or CWs) capable ofbeing maximally received in one subframe at a CC^(C). TB_(max)(C) is setto 1 or 2, the number of ACK/NACK bits can be represented by thefollowing equation 3.

$\begin{matrix}{O_{{HARQ} - {ACK}} = {{\max \; {{PDCCHperCC} \cdot {\sum\limits_{c = 0}^{C - 1}\; {{TB}_{\max}(c)}}}} = {\max \; {{PDCCHperCC} \cdot \left( {C + C_{2}} \right)}}}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

In Equation 3, C₂ is the number of CCs in which a maximum of 2 TBs canbe transmitted in one subframe. If spatial bundling is applied to N CCs,C₂ is replaced with C₂-N. Therefore, if the spatial bundling is appliedto all CCs, C₂ is set to zero (C₂=0).

FIGS. 19 and 20 exemplarily show other ACK/NACK transmission processes.Similar to FIG. 18, FIGS. 19 and 20 assume a TDD system in which 4 CCsare aggregated and the ratio of DL SF and UL SF is denoted by “DL SF:ULSF=4:1”, and ‘maxPDCCHperCC’ is indicated under a TDD situation. FIG. 19exemplarily shows the case in which the BS further considers ‘PDSCH w/oPDCCH’ so as to determine ‘maxPDCCHperCC’ (i.e., maxPDCCHperCC=3).Therefore, the UE may configure ACK/NACK payload in consideration of notonly PDSCHs corresponding to ‘DAI-c=0˜2’ for each DL CC but alsoassociated ACK/NACK positions. In more detail, the UE may locateACK/NACK for a PDSCH corresponding to ‘DAI-c=x (x=0˜2)’ at the ACK/NACKposition corresponding to ‘DAI-c=x’, such that it can configure ACK/NACKpayload. Therefore, although a PDSCH corresponding to ‘DAI-c=2’ is notscheduled, ACK/NACK bits must be unnecessarily filled in such a mannerthat overhead may increase. On the other hand, FIG. 20 shows anexemplary case in which the BS does not consider ‘PDSCH w/o PDCCH’ whendetermining ‘maxPDCCHperCC’ (i.e., maxPDCCHperCC=2). Accordingly, the UEmay add ACK/NACK bits for ‘PDSCH w/o PDCCH’ to ACK/NACK bits that areconfigured considering not only PDSCHs corresponding to ‘DAI-c=0˜1’ foreach DL CC but also associated ACK/NACK positions, such that theACK/NACK payload can be configured.

FIG. 21 exemplarily shows another ACK/NACK transmission processaccording to the present invention. The ACK/NACK transmission processshown in FIG. 21 may consider a method for signaling a maximum valuefrom among the number of PDSCHs scheduled/transmitted for DL CCs otherthan a PCC under the condition that the DAI-counter is not present in aPDCCH that schedules the PCC. In this case, the UE may configureACK/NACK payload for all DL SFs in association with a PCC. In contrast,in association with each DL CC other than a PCC, the UE may configureACK/NACK payload considering not only a PDSCH (or PDCCH) ranging from aninitial value for each DL CC to a DAI-counter value (i.e., DAI-c)corresponding to ‘maxPDCCHperCC−1’ (where the DAI-counter starts from 0)or ‘maxPDCCHperCC’ (where the DAI-counter starts from 1), but alsoassociated ACK/NACK positions, such that it can configure the ACK/NACKpayload.

Referring to FIG. 21, the UE may configure ACK/NACK payload for all fourDL SFs in association with a PCC. On the other hand, since‘maxPDCCHperCC’ related to DL CCs other than a PCC is set to 2, the UEcan configure ACK/NACK payload in consideration of a PDSCH (or PDCCH)corresponding to ‘DAI-c=0˜1’ and its associated ACK/NACK position. Inmore detail, ACK/NACK for a PDSCH corresponding to ‘DAI-c=x (x=0˜1)’ islocated at the ACK/NACK position corresponding to ‘DAI-c=x’ so as toconfigure ACK/NACK payload.

The above-mentioned ACK/NACK piggyback scheme based on UL DAI signalingfor ‘maxPDCCHperCC’ may be appropriate for the case in which DLscheduling is relatively and uniformly carried out in all CCs. In otherwords, if DL scheduling is performed (or concentrated) only in one CC ora small number of CCs, an unnecessarily high ‘maxPDCCHperCC’ value maybe applied to all CCs. In this case, unnecessary overhead may occur dueto the number of ACK/NACK modulation symbols contained in a PUSCH or thenumber of REs used for ACK/NACK transmission.

Therefore, the present invention may employ a method for adjusting thenumber of REs used for ACK/NACK transmission in a PUSCH through a ULgrant PDCCH (e.g., the use of UL DAI field) but not through the numberof piggybacked ACK/NACK payload bits. Equation 4 shows the number ofcoded modulation symbols for HARQ-ACK on the condition that one UL-SCHtransport block (TB) is transmitted on a UL CC. Equation 5 shows thenumber of coded modulation symbols for HARQ-ACK on the condition thattwo UL-SCH TBs are transmitted on a UL CC. The number of codedmodulation symbols for HARQ-ACK is equivalent to the number of REs forHARQ-ACK.

$\begin{matrix}{Q^{\prime} = {\min \begin{pmatrix}{\left\lceil \frac{O \cdot M_{sc}^{{PUSCH} - {initial}} \cdot N_{symb}^{{PUSCH} - {initial}} \cdot \beta_{offset}^{PUSCH}}{\sum\limits_{r = 0}^{C - 1}\; K_{r}} \right\rceil,} \\{4 \cdot M_{sc}^{PUSCH}}\end{pmatrix}}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack \\{\mspace{79mu} {{Q^{\prime} = {\max \left\lbrack {{\min \left( {Q_{temp}^{\prime},{4 \cdot M_{sc}^{PUSCH}}} \right)},Q_{\min}^{\prime}} \right\rbrack}}{Q_{temp}^{\prime} = \left\lceil \frac{\begin{matrix}{O \cdot M_{sc}^{{PUSCH} - {{initial}{(1)}}} \cdot N_{symb}^{{PUSCH} - {{initial}{(1)}}} \cdot} \\{M_{sc}^{{PUSCH} - {{initial}{(2)}}} \cdot N_{symb}^{{PUSCH} - {{initial}{(2)}}} \cdot \beta_{offset}^{PUSCH}}\end{matrix}}{\begin{matrix}{{\sum\limits_{r = 0}^{C^{(1)} - 1}\; {K_{r}^{(1)} \cdot M_{sc}^{{PUSCH} - {{initial}{(2)}}} \cdot N_{symb}^{{PUSCH} - {{initial}{(2)}}}}} +} \\{\sum\limits_{r = 0}^{C^{(2)} - 1}\; {K_{r}^{(2)} \cdot M_{sc}^{{PUSCH} - {{initial}{(1)}}} \cdot N_{symb}^{{PUSCH} - {{initial}{(1)}}}}}\end{matrix}} \right\rceil}}} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

In Equations 4 and 5, Q′ is the number of coded modulation symbols foreach layer, and O is the number of HARQ-ACK bits. M_(sc) ^(PUSCH) is aband (on a subcarrier basis) scheduled for PUSCH transmission of atransport block (TB) in a current subframe. M_(sc) ^(PUSCH-initial) is aband (on a subcarrier basis) scheduled for initial PUCCH transmission.N_(symb) ^(PUSCH-Intial) is the number of SC-FDMA symbols per subframefor initial PUSCH transmission of the same transport block (TB), asrepresented by N_(symb) ^(PUSCH-Intial)=(2·(N_(symb) ^(UL)−1)−N_(SRS)).N_(symb) ^(UL) is the number of SC-FDMA symbols in a UL slot. N_(SRS)for SRS transmission is set to 0 or 1. β_(offset) ^(PUSCH) is an offsetvalue. C is the number of code blocks associated with the same transportblock (TB), K_(r) is a payload size of the code block (r). Superscriptmay indicate a layer number, and Q′_(min) is the lower limit of thecoded modulation symbol.

In the above-mentioned scheme, the number (O^(ACK)) of ACK/NACK payloadpiggybacked on a PUSCH under a TDD of ‘DL SF:UL SF=M:1’ can berepresented by the following equation 6, irrespective of the UL DAIvalue.

O ^(ACK) =M(C+C ₂)  [Equation 6]

In Equation 6, C is the number of CCs, and C₂ is the number of CCs inwhich a transmission mode is established to support transmission of amaximum of 2 TBs and spatial bundling is not applied.

The number of REs used for ACK/NACK transmission in a PUSCH can beadjusted according to the received UL DAI value, and a detaileddescription thereof is as follows. In more detail, in the case of usinga UL UAI composed of N bits (i.e., a UL UAI capable of expressing 2^(N)states), a parameter O shown in Equations 4 and 5 can be calculatedusing 2^(N) values (where 2 ^(N)≦O^(ACK)) according to the UL DAI value.Differently from the scheme that determines the number of bits ofACK/NACK payload on the basis of the ‘maxPDCCHperCC’ value, the presentinvention can adjust the number of ACK/NACK transmission REs containedin a PUSCH through UL DAI signaling. Therefore, 2^(N) UL DAI values maybe utilized irrespective of the M value.

For example, provided that N-bit UL DAI is denoted by V_(DAI) ^(UL)ε{1,. . . , 2^(N)}, the parameter O depending on the received UL DAI valuecan be represented by the following equation 7.

$\begin{matrix}{O = {{\frac{V_{DAI}^{UL}}{2^{N}} \cdot O^{ACK}} = {\frac{V_{DAI}^{UL}}{2^{N}} \cdot {M\left( {C + C_{2}} \right)}}}} & \left\lbrack {{Equation}\mspace{14mu} 7} \right\rbrack\end{matrix}$

Provided that 2-bit UL DAI is denoted by V_(DAI) ^(UL)ε{1, 2, 3, 4} theparameter O depending on the received UL DAI can be represented by thefollowing equation 8.

$\begin{matrix}{O = {{\frac{V_{DAI}^{UL}}{4} \cdot O^{ACK}} = {\frac{V_{DAI}^{UL}}{4} \cdot {M\left( {C + C_{2}} \right)}}}} & \left\lbrack {{Equation}\mspace{14mu} 8} \right\rbrack\end{matrix}$

On the other hand, one or more PUSCHs may be transmitted through one ormore CCs in a specific UL SF of the CA based TDD system, and a PUSCH(i.e., PUSCH w/o PDCCH, for example, SPS PUSCH) transmitted withoutscheduling caused by a UL grant PDCCH may also be contained in one ormore PUSCHs. Under this situation, if PUSCH w/o PDCCH is selected forACK/NACK piggyback, it is preferable that ACK/NACK be piggybacked to thecorresponding PUSCH using a maximum value (i.e., O=O^(ACK)=M (C+C₂))capable of being assigned to a UL DAI.

Method 2) First or Last PDSCH (PDCCH)—Scheduled DL CC Indication

In association with a DL SF group corresponding to a UL SF, Method 2 caninform a UE of the first DL CC index (F-SC index) or the last DL CCindex (F-CC index) in which at least one PDSCH (or DL grant PDCCH) isscheduled/transmitted for a DL SF group corresponding to a UL SF,through a UL grant PDCCH. The UE can transmit ACK/NACK through a PUSCHon the corresponding UL SF. In this case, a PDSCH (e.g., SPS PDSCH)transmitted without using a PDCCH is known to both the BS and the UE,such that it may be excluded from a PDSCH that decides F-CC or L-CCindex. In more detail, when indicating the F-CC index, the UE mayconfigure ACK/NACK payload only for DL CCs ranging from thecorresponding F-CC index to the last F-CC index. Alternatively, whenindicating the L-CC index, the UE may configure ACK/NACK payload onlyfor DL CCs ranging from the first CC index to the corresponding L-CCindex. CC corresponding to the first CC index may be a primary CC.

In addition, CC index information may be transmitted through a DAI fieldcontained in a UL grant PDCCH. The UL grant PDCCH may include“no-PDSCH-state” indication information that indicates the absence ofPDSCH (or DL grant PDCCH) scheduling/transmission in the entire DL SFgroup corresponding to a UL SF. The “no-PDSCH-state” indicationinformation may be transmitted through the DAI field of the UL grantPDCCH. In this case, CC index information and “no-PDSCH-state”indication information may be distinguished from each other by differentbits of the DAI field or different DAI states, or may share a specificDAI state. Specifically, if F-CC and L-CC from among several DL CCindexes are present, DL CCF having the lowest/highest index from amongthe corresponding DL CC indexes may be indicated by F/L-CC index.

FIG. 22 is a conceptual diagram illustrating an exemplary ACK/NACKpayload configuration on the condition that four CCs are aggregated andDL SFs and UL SFs are configured in the ratio of ‘DL SF:UL SF=4:1’.Referring to FIG. 22, L-CC (i.e., DL CC #3) in which at least one PDSCHis scheduled/transmitted may be indicated through the UL grant PDCCH.Specifically, when considering 2-bit DAI to indicate an L-CC index, ifDL CC #3 or #4 denotes L-CC, L-CC index may be identical to DL CC #4(i.e. L-CC index=DL CC #4).

In another example, the present invention may indicate each DL CC indexin which at least one PDSCH (or DL grant PDCCH) isscheduled/transmitted, in the form of bitmap information.

Method 3) First or Last PDSCH (PDCCH)—Scheduled ACK/NACK GroupIndication

Method 3 can inform a UE of the first ACK/NACK group index (F-ANG index)or the last ACK/NACK group index (L-ANG index) in which at least onePDSCH (or DL grant PDCCH) is scheduled/transmitted, through a PDCCH thatschedules a PUSCH to be transmitted through the corresponding UL SF. TheACK/NACK group may correspond to a DL CC group, a DL SF group, or acombination thereof, and an index is pre-assigned to each ACK/NACKgroup.

PDSCH w/o PDCCH (for example, SPS PDSCH) is known to the BS and the UE,such that the ‘PDSCH w/o PDCCH’ information can be excluded from a PDSCHfor F- or L-ANG index decision. In more detail, when indicating theF-ANG index, the UE may configure ACK/NACK payload only for DLsubframes/DL CCs corresponding to indexes from the F-ANG index to thelast ANG index. Similarly, when indicating the L-ANG index, the UE mayconfigure ACK/NACK payload only for DL subframes/DL CCs corresponding toindexes from the first ANG index to the L-ANG index.

In addition, ANG index information may be transmitted through a DAIfield contained in a UL grant PDCCH. The UL grant PDCCH may include“no-PDSCH-state” indication information that indicates the absence ofPDSCH (or DL grant PDCCH) scheduling/transmission in the entire DL SFgroup corresponding to a UL SF. The “no-PDSCH-state” indicationinformation may be transmitted through the DAI field of the UL grantPDCCH. In this case, ANG index information and “no-PDSCH-state”indication information may be distinguished from each other by differentbits of the DAI field or different DAI states, or may share a specificDAI state. Specifically, if F-ANG and L-ANG from among several ANGindexes are present, ANG having the lowest/highest index from among thecorresponding ANG indexes may be indicated by F/L-ANG index.

FIG. 23 is a conceptual diagram illustrating an exemplary ACK/NACKpayload configuration based on L-ANG index indication on the conditionthat four CCs are aggregated and DL SFs and UL SFs are configured in theratio of ‘DL SF:UL SF=4:1’. Referring to FIG. 23, L-ANG (i.e., ACK/NACKgroup #2) in which at least one PDSCH is scheduled/transmitted may beindicated through the UL grant PDCCH. The UE may configure ACK/NACKconfiguration only for DL subframes/DL CCs (i.e., DL SF #1 and DL SF#2/DL CCs #1 to #4) corresponding to the ACK/NACK groups #1 and #2.

In another example, the present invention may indicate each ACK/NACKgroup index in which at least one PDSCH (or DL grant PDCCH) isscheduled/transmitted, in the form of bitmap information.

Method 4) ACK/NACK Payload Corresponding to ACK/NACK Group Indication

In association with a DL SF group corresponding to a UL SF, Method 4 caninform a UE of the ACK/NACK group index (i.e., AN-PG index) serving asan ACK/NACK payload configuration target, through a PDCCH that schedulesa PUSCH to be transmitted through the corresponding UL SF. The ACK/NACKgroup may correspond to a DL CC group, a DL SF group, or a combinationthereof, and an index is pre-assigned to each ACK/NACK group. PDSCH w/oPDCCH (for example, SPS PDSCH) is known to the BS and the UE, such thatSPS PDCCH may be excluded from a PDSCH for AN-PG index decision. InMethod 4, the UE may directly configure ACK/NACK payload only for anACK/NACK group corresponding to the AN-PG index.

In addition, AN-PG index information may be transmitted through a DAIfield contained in a UL grant PDCCH. The UL grant PDCCH may include“no-PDSCH-state” indication information that indicates the absence ofPDSCH (or DL grant PDCCH) scheduling/transmission in the entire DL SFgroup corresponding to a UL SF. The “no-PDSCH-state” indicationinformation may be transmitted through the DAI field of the UL grantPDCCH. In this case, AN-PG index information and “no-PDSCH-state”indication information may be distinguished from each other by differentbits of the DAI field or different DAI states, or may share a specificDAI state.

FIG. 24 is a conceptual diagram illustrating an exemplary ACK/NACKpayload configuration based on AN-PG index indication on the conditionthat four CCs are aggregated and DL SFs and UL SFs are configured in theratio of ‘DL SF:UL SF=4:1’. Referring to FIG. 24, AN-PG (i.e., ACK/NACKgroup #2) including all PDSCH scheduling/transmission may be indicatedthrough the UL grant PDCCH. The UE may configure ACK/NACK configurationonly for DL subframes/DL CCs (i.e., DL SF #3 and DL SF #4/DL CCs #1 to#4) corresponding to the ACK/NACK group #2.

During ACK/NACK grouping for Method 4, it is preferable that an ACK/NACKgroup (i.e., ACK/NACK group #3 shown in FIG. 24) including all DL CCsand all DL SFs may be preferably indicated. In addition, PCC and SCC(s)are distinguished from each other so as to indicate different ACK/NACKgroups, and can also indicate different ACK/NACK groups according to thepresence or absence of CW bundling.

In accordance with the above-mentioned methods, one common method can beapplied to all UEs through a cell-specific method configuration, orindependent methods can be applied to individual UEs through aUE-specific method configuration.

As can be seen from the above-mentioned methods, if an ACK/NACK payloadsection (i.e., signaled ACK/NACK payload) to be piggybacked to a PUSCHusing information signaled via a UL grant PDCCH (e.g., via a UL DAIfield), ACK/NACK for PDSCH w/o PDCCH can be processed as follows. In theabove-mentioned signaling information, PDSCH w/o PDCCH (for example, SPSPDSCH) may be excluded from the process for determining thecorresponding information. For convenience of description, each DL SFcontained in one DL CC is referred to as a slot.

1) Case in which a slot to which ‘PDSCH w/o PDCCH’ isscheduled/transmitted is present in the signaled ACK/NACK payload:

-   -   After ACK/NACK for the corresponding PDSCH is mapped to the        corresponding slot contained in the signaled ACK/NACK payload,        the signaled ACK/NACK payload is piggybacked to a PUSCH.

2) Case in which a slot to which ‘PDSCH w/o PDCCH’ isscheduled/transmitted is not present in the signaled ACK/NACK payload,or Case of Method 1-A:

-   -   ACK/NACK for the corresponding PDSCH is mapped by newly adding        an MSB (or LSB) to the signaled ACK/NACK payload and the mapped        result is then piggybacked to a PUSCH. In this case, the term        ‘LSB’ may be an LSB for either the entire signaled ACK/NACK        payload or a PCC ACK/NACK part contained in the signaled        ACK/NACK payload.

On the other hand, the CA based TDD system may transmit one or morePUSCHs through one or more UL CCs at a specific UL SF, and PUSCH w/oPDCCH (for example, SPS PUSCH) may also be contained in one or morePUSCHs. For convenience of description, a general PUSCH (i.e., a PUSCHscheduled/transmitted by a UL grant PDCCH) will hereinafter be referredto as PUSCH w/ PDCCH′. Under this condition, if it is necessary forACK/NACK to be piggybacked on a PUSCH, only one PUSCH is selected fromamong one or more PUSCHs, such that such ACK/NACK information can bepiggybacked and transmitted only to a specific PUSCH. If the selectedspecific PUSCH is PUSCH w/o PDCCH′, there is no information signaled viaa UL grant PDCCH (e.g., via a DAI field), such that the UE operation canbe defined as follows so as to decide the piggybacked ACK/NACK payload.

<Alt 1a>

1) Under the condition that PUSCH w/ PDCCH′ does not exist and onlyPUSCH w/o PDCCH′ exists, if PUSCH w/o PDCCH′ is selected for ACK/NACKpiggyback, ACK/NACK payload is configured for all DL SFs and all DL CCsaggregated by a UE, such that the resultant ACK/NACK information ispiggybacked to the selected PUSCH.

2) Under the condition that PUSCH w/ PDCCH′ and PUSCH w/o PDCCH′ arepresent and PUSCH w/o PDCCH′ is selected for ACK/NACK piggyback,ACK/NACK payload is configured on the basis of information signaledthrough a UL grant PDCCH (for example, via a DAI field) of PUSCH w/PDCCH′, such that the resultant ACK/NACK information is piggybacked tothe selected PUSCH.

<Alt 1b>

1) If PUSCH w/o PDCCH′ is selected for ACK/NACK piggyback on thecondition that PUSCH w/o PDCCH′ exists, ACK/NACK payload is configuredfor all DL SFs and all DL CCs aggregated by the UE, irrespective of thepresence or absence of PUSCH w/ PDCCH′, such that the resultant ACK/NACKinformation is piggybacked to the selected PUSCH.

On the other hand, information (i.e., TDD-UL-DAI) signaled through a ULgrant PDCCH (for example, via a DAI field) to determine the piggybackedACK/NACK payload may be preferably set to the same value in UL grantPDCCH(s) scheduling several PUSCHs at a specific UL SF so as to preventinconsistency in piggybacked ACK/NACK payload between the UE and the BS.If TDD-UL-DAI values are different in UL grant PDCCH(s) corresponding toa specific UL SF, the UE operation can be defined as follows.

<Alt 2a>

If TDD-UL-DAI values are different in all UL grant PDCCHs, thecorresponding UL grant PDCCHs are discarded, and a PUSCH correspondingto the discarded PDCCHs is not transmitted. Based on the above-mentionedsituation, a detailed operation for ACK/NACK piggyback can be defined asfollows.

1) If PUSCH w/o PDCCH′ is selected for ACK/NACK piggyback on thecondition that different TDD-UL-DAI values are assigned to all UL grantPDCCHs, the corresponding UL grant PDCCHs are discarded (for example,PUSCH transmission scheduled by the corresponding UL grant PDCCHs iscompletely dropped), ACK/NACK payload for all DL SFs and all DL CCsaggregated by the UE is configured, such that the resultant ACK/NACKinformation is piggybacked on PUSCH w/o PDCCH′.

2) If PUSCH w/o PDCCH′ is not selected for ACK/NACK piggyback under thecondition that different TDD-UL-DAI values are assigned to all UL grantPDCCHs and PUSCH w/o PDCCH′ exists, the corresponding UL grant PDCCHsare discarded (for example, PUSCH transmission scheduled by thecorresponding UL grant PDCCHs is completely dropped), and the sameACK/NACK piggyback as in <Alt 2a-1> is performed through ‘PUSCH w/oPDCCH’.

3) Under the condition that different TDD-UL-DAI values are assigned toall UL grant PDCCHs and PUSCH w/o PDCCH′ does not exists, thecorresponding UL grant PDCCHs are discarded (for example, PUSCHtransmission scheduled by the corresponding UL grant PDCCHs iscompletely dropped), such that the resultant ACK/NACK information istransmitted through a PUCCH without being piggybacked to a PUSCH.

<Alt 2b>

1) If PUSCH w/o PDCCH′ is selected for ACK/NACK piggyback on thecondition that different TDD-UL-DAI values are assigned to all UL grantPDCCHs, ACK/NACK payload is configured for all DL SFs and all DL CCsaggregated by the UE, without additional processing (e.g., UL grantPDCCH is discarded), such that the resultant ACK/NACK information ispiggybacked to the selected PUSCH.

2) Under the condition that different TDD-UL-DAI values are assigned toall UL grant PDCCHs and PUSCH w/o PDCCH′ exists, the corresponding ULgrant PDCCHs are discarded (for example, PUSCH transmission scheduled bythe corresponding UL grant PDCCHs is completely omitted), the sameACK/NACK piggyback as in the <Alt 2b-1> scheme is carried out throughPUSCH w/o PDCCH′.

3) Under the condition that different TDD-UL-DAI values are assigned toall UL grant PDCCHs and PUSCH w/o PDCCH′ does not exist, thecorresponding UL grant PDCCHs are discarded (for example, PUSCHtransmission scheduled by the corresponding UL grant PDCCHs iscompletely omitted), and ACK/NACK is transmitted through a PUCCH withoutbeing piggybacked to a PUSCH.

Embodiment 3

Embodiment 3 shows a method for reducing the size of ACK/NACK payloadpiggybacked to a PUSCH using the UL DAI field in the CA based TDDsystem. As can be seen from FIGS. 12 to 21, a DAI field (DL DAI)contained in the DL grant PDCCH is used as a counter indicatinginformation about the number of PDSCHs, and a DAI field (UL DAI)contained in the UL grant PDCCH indicates a total number of PDSCHstransmitted during the DL subframe, such that the number of payloadpiggybacked to a PUSCH can be dynamically adjusted. In this case, thenumber of PDSCHs is equivalent to the number of DL SFs for whichACK/NACK feedback is needed.

FIG. 25 exemplarily shows the ACK/NACK transmission process depending onwhether or not UL DAI is used. For convenience of description and betterunderstanding of the present invention, it is assumed that TDD and oneCC are aggregated as shown in FIG. 25.

Referring to FIG. 25, a base station (BS) transmits PDCCH and PDSCH(PDCCH/PDSCH) at DL SF#1, DL SF#3, and DL SF#4. Information indicatingthe order value of the corresponding PDCCH is included in a DAI field ofeach DL grant PDCCH. In FIG. 25, it is assumed that the UE fails todetect a PDCCH (DL DAI=3) at a subframe (SF #4) (i.e., in case of theoccurrence of PDCCH DTX). In this case, provided that information of atotal number of UL DAIs is not in use, the UE must feed back ACK/NACKduring a maximum of 4 SFs due to the PDCCH DTX problem. However,provided that the UE recognizes information of a total number of ULDAIs, the amount of ACK/NACK payload to be piggybacked to a PUSCH can bereduced as shown in FIG. 25. In addition, since the UE receives a PDSCHonly at SF #1 and SF #3, it transmits ACK/NACK at bit positionscorresponding to SF #1 and SF #3 within ACK/NACK payload, and the bitposition corresponding to a specific SF where a PDSCH is not received isfilled with NACK states, such that the UE can transmit the resultantinformation.

Considering a TDD situation in which a plurality of CCs is aggregated,the following scheme can be used as the extended version of theabove-mentioned scheme.

FIG. 26 exemplarily shows the ACK/NACK transmission process depending onwhether or not UL DAI is used. For convenience of description and betterunderstanding of the present invention, it is assumed that DL SFs and ULSFs are aggregated in the ratio of DL SF:UL SF=4:1 and three CCs areaggregated.

Referring to FIG. 26, a BS may inform a UE of a maximum number of PDSCHsor a maximum value of the numbers of DL scheduling PDCCHs transmittedper CC through the UL DAI. In this case, the UE may configure ACK/NACKpayload based on the UL DAI value per CC as shown in Equations 2 and 3.For example, if the UE aggregates three CCs, each of which isestablished in a non-MIMO mode, and a value indicated by the UL DAI isset to 3, 3 bits must be scheduled per CC so that payload composed of 9bits can be configured.

Considering the above-mentioned scheme, the present invention provides amethod for configuring a UL DAI state under a UL DAI composed of alimited number of bits (e.g., 2 bits). For example, when considering thecase in which DL SFs and UL SFs are aggregated in the ratio of ‘DL SF:ULSF=4:1’ in the TDD system, information mapped to a UL DAI can express upto 5 states (i.e., 0, 1, 2, 3, and 4) (i.e., a maximum value among thenumbers of PDSCHs transmitted per CC or a maximum value among thenumbers of DL grant PDCCHs transmitted per CC). However, if the DAIfield is composed of 2 bits, the number of bits is insufficient.Therefore, it is necessary to overlap the UL DAI states, and it is alsonecessary to define the UE operation for the overlapped UL DAI states.

For example, the present invention may provide a method for mapping twocontiguous values to one UL DAI state at the UL DAI mapping information(i.e., 0, 1, 2, 3, 4).

Table 8 exemplarily shows a UL DAI state mapping table.

TABLE 8 UL DAI Information mapped to Information mapped to state UL DAIUL DAI A 0

0 B 1,2 2 C 3 3 D 4 4

In Table 8, A, B, C, and D may be elements of {00, 01, 10, 11} bits. Forexample, A, B, C and D can be mapped to one another in various ways, forexample, {A=00, B=01, B=10, D=11}, {A=01, B=10, C=11, D=00}, etc.

For explanation of the operations shown in Table 8, it is assume thatthe UE receives the UL DAI field value corresponding to ‘UL DAI state=B’through the UL grant PDCCH. In this case, the UE assumes that the numberof DL subframes requiring ACK/NACK feedback is set to 2, whereas thenumber of DL subframes (i.e., a maximum number of PDCCHs/PDSCHs capableof being transmitted) requiring ACK/NACK feedback at a CC may be set to1 or 2, such that the resultant ACK/NACK payload is configured. In otherwords, provided that the UE configures three MIMO CCs and does not usespatial bundling, the UE may configure ACK/NACK payload composed of atotal of 12 bits (i.e., 4-bit ACK/NACK payload per CC).

Similarly, 2 and 3 from among information mapped to UL DAI areaggregated so that the aggregated result may be mapped to one UL DAIstate, and 3 and 4 from among information mapped to UL DAI areaggregated so that the aggregated result may be mapped to one UL DAIstate.

Table 9 shows another example for constructing the UL DAI state mappingtable. Table 9 exemplarily shows a method for mapping ‘0’ and ‘4’ fromamong the UL DAI mapping information (i.e., 0, 1, 2, 3, 4) to one UL DAIstate.

TABLE 9 UL DAI Information mapped to Information mapped to state UL DAIUL DAI A 0,4

0 or 4 (conditional mapping) B 1 1 C 2 2 D 3 3

In Table 9, A, B, C, and D may be elements of {00, 01, 10, 11} bits. Forexample, A, B, C and D can be mapped to one another in various ways, forexample, {A=00, B=01, B=10, D=11}, {A=01, B=10, C=11, D=00}, etc.

For explanation of the operations shown in Table 9, it is assume thatthe UE receives the UL DAI field value corresponding to ‘UL DAI state=A’through the UL grant PDCCH. In this case, if at least one DL schedulingPDCCH (including SPS release PDCCH) or PDSCH is detected in a pluralityof DL SFs corresponding to UL SF, the UE recognizes informationindicated by the corresponding UL DAI state as the value of 4, andconfigures ACK/NACK payload as described above. In other words, providedthat a UL DAI state is set to A, if DL scheduling PDCCH (including SPSrelease PDCCH) and PDSCH are not detected in a plurality of DL SFscorresponding to UL SF, the UE may recognize information indicated bythe corresponding UL DAI state as zero ‘0’, and may not piggybackACK/NACK to a PUSCH. That is, the UE may not transmit ACK/NACK over aPUDSCH.

Table 10 shows another example of a UL DAI state mapping table. Table 10exemplarily shows a method for mapping ‘1’ and ‘4’ from among UL DAImapping information (i.e., 0, 1, 2, 3, 4) to one UL DAI state.

TABLE 10 UL DAI Information mapped to Information mapped to state UL DAIUL DAI A 0

0 B 1,4 1 or 4 (conditional mapping) C 2 2 D 3 3

A, B, C, and D may be elements of {00, 01, 10, 11} bits. For example, A,B, C and D can be mapped to one another in various ways, for example,{A=00, B=01, B=10, D=11}, {A=01, B=10, C=11, D=00}, etc.

For explanation of the operations shown in Table 10, it is assume thatthe UE receives the UL DAI field value corresponding to ‘UL DAI state=B’through the UL grant PDCCH. In this case, if at least two DL schedulingPDCCHs (each of which includes SPS release PDCCH) or PDSCHs are detectedin at least one CC, the UE recognizes information indicated by thecorresponding UL DAI state as ‘4’, and configures ACK/NACK payload asdescribed above. In other words, provided that a UL DAI state is set toB, if one or less DL scheduling PDCCH (including SPS release PDCCH) orPDSCH is detected in at least one CC, the UE may recognize informationindicated by the corresponding UL DAI state as ‘1’, and may configureACK/NACK payload.

Embodiment 4

The problem encountered when ACK/NACK payload including ACK/NACK for aPUSCH (e.g., SPS PDSCH) transmitted without a corresponding PDCCH isconfigured will hereinafter be described with reference to FIG. 27.Embodiment 4 exemplarily shows a TDD situation in which multiple CCs areaggregated. For convenience of description and better understanding ofthe present invention, it is assumed that PDSCH and/or PDCCH(PDSCH/PDCCH) are transmitted in one DL CC. The example shown in FIG. 27may be applied to an FDD in which multiple CCs are aggregated.

Referring to FIG. 27, the BS transmits a PDSCH at DF SFs #1, #2 and #4,and transmits SPS PDSCH at DL SF #2. For convenience of description andbetter understanding of the present invention, it is assumed that the UEdoes not receive a PDCCH at DL SF #2 and DL SF #4. In this case, asdescribed above, when the ACK/NACK payload size is dynamically adjustedusing a UL DAI, the position of ACK/NACK for SPS PDSCH becomesambiguous. In more detail, in the case of SPS scheduling, if SPS isactivated through PDCCH, a PDSCH is transmitted without a PDCCH atintervals of a predetermined time promised between the BS and the UE. Asdescribed above, if PDSCH is transmitted without a PDCCH, the ordervalue of PDSCH is not transmitted such that it is impossible torecognize the position/order of ACK/NACK for the corresponding PDSCH.

Therefore, in the case of using ACK/NACK (that may be composed of one ortwo bits according to a transmission mode (i.e., a maximum number of CWscapable of being transmitted) of a DL CC to which SPS PDSCH is allocatedand the presence or absence of CW bundling) for SPS PDSCH, in order toprevent inconsistency in ACK/NACK bit position between the UE and theBS, the present invention proposes a method for mapping SPS PDSCHACK/NACK (referred to as SPS PDSCH A/N) to a fixed position within theACK/NACK payload. ACK/NACK payload may be transmitted over a PUSCH orPUCCH. For example, the fixed position for SPS PDSCCH A/N may include anMSB or LSB within ACK/NACK payload. In this case, LSB may be an LSB foreither the entire ACK/NACK payload or a PCC ACK/NACK part (i.e., per-CCACK/NACK payload for PCC) contained in ACK/NACK payload. If the lowestPCC cell index is established, LSB may be an LSB for an ACK/NACK part ofa specific cell having the lowest cell index within ACK/NACK part.Similarly, MSB may be an MSB for the entire ACK/NACK payload or a PCCACK/NACK part contained in ACK/NACK payload. If the lowest PCC cellindex is established, MSB may be an MSB for an ACK/NACK part of aspecific cell having the lowest cell index within ACK/NACK part.

FIGS. 28 and 29 exemplarily show a method for configuring ACK/NACKpayload according to one embodiment of the present invention. FIG. 28exemplarily shows an FDD situation in which multiple CCs are aggregated.In the FDD system, a DL subframe is mapped to a UL subframe on a one toone basis, such that ACK/NACK for one DL subframe is transmitted on asingle UL subframe. FIG. 29 exemplarily shows a TDD situation in whichmultiple CCs are aggregated. In the TDD system, a DL subframe is mappedto a UL subframe on M to one basis, such that ACK/NACK for multiple DLsubframes can be transmitted on a single UL subframe.

Referring to FIGS. 28 and 29, the following three options may beselectively used.

Option A: SPS PDSCH A/N may be located at the end of ACK/NACK payload.That is, SPS PDCCH A/N may be located at LSB of the ACK/NACKconfiguration bits. In accordance with the present option, ACK/NACK towhich the order value contained in a DAI is assigned may be arranged asan order value without change. SPS PDSCH A/N is arranged after ACK/NACKof a PDSCH (and SPS release PDCCH) witha corresponding PDCCH. Ifmultiple SPS PDSCHs are present, multiple SPS PDSCH A/N signals may alsobe arranged from the position of LSB. Preferably, SPS PDSCH A/Ns may bearranged in ascending numerical order (or in descending numerical order)of CC index of SPS PDSCH, and may be arranged in ascending numericalorder (or in descending numerical order) of subframe number in a case ofthe same CC indexes.

Option B: SPS PDSCH A/N may be located at the front of ACK/NACK payload.That is, SPS PDSCH A/N may be located at MSB of the ACK/NACKconfiguration bit. According to the present option, since SPS PDSCH A/Nis located at the front of the ACK/NACK payload, such that ACK/NACK towhich the order value contained in a DAI is assigned must be shiftedbackward one by one within the ACK/NACK payload. If SPS is transmittedto a specific CC, ACK/NACK payload for the corresponding CC can alwaysbe located at the front of the entire ACK/NACK payload. As shown in thedrawings, if per-cell ACK/NACK payload is sequentially concatenated inthe order of CC index so as to configure the entire ACK/NACK payload,the lowest CC index may be assigned to a CC having SPS PDSCH, or SPSPDSCH may be transmitted only through a CC having the lowest CC index.For example, a specific CC including SPS PDSCH may be limited to aprimary CC. If multiple SPS PDSCHs are present, multiple SPS PDSCH A/Nsignals may also be arranged from the position of MSB. Preferably, SPSPDSCH A/Ns may be arranged in ascending numerical order (or indescending numerical order) of CC index of SPS PDSCH, and may bearranged in ascending numerical order (or in descending numerical order)of subframe number in a case of the same CC indexes.

Option C: SPS PDSCH A/N may be located at the last position of ACK/NACKpayload for a CC including SPS PDSCH. That is, SPS PDSCH A/N may belocated at LSB of per-CC ACK/NACK configuration bit. If multiple SPSPDSCHs are present, multiple SPS PDSCHs may be arranged from theposition of LSB of per-CC ACK/NACK configuration bit field. Preferably,the SPS ACK/NACKs may be located at each CC index of SPS PDSCH, and thesame CC indexes may be arranged in ascending numerical order (or indescending numerical order) of subframe number in a case of the same CCindexes.

FIG. 30 shows another example of ACK/NACK payload configuration. FIG. 30shows an example of the above-mentioned option C shown in FIG. 19.

A detailed description of FIG. 19 will hereinafter be described withreference to FIG. 30. According to the scheme of FIG. 19, the UE mayadjust the entire ACK/NACK payload size using a UL DAI value. In moredetail, the UE can determine the size of per-CC ACK/NACK payload (i.e.,ACK/NACK part) for each DL CC in consideration of a UL DAI value, atransmission mode of the corresponding CC, and the presence or absenceof bundling. In addition, the UE can determine the position of eachACK/NACK within per-CC ACK/NACK payload using DL DAI value(s) receivedat each DL CC.

In more detail, it is assumed that the HARQ-ACK feedback bit for thec-th DL CC (or serving cell) is defined as

o_(c, 0)^(ACK)o_(c, 1)^(ACK), …  , o_(c, O_(c)^(ACK) − 1)^(ACK)

(where c≧0). O_(c) ^(ACK) is the number (i.e., size) of HARQ-ACK payloadbits for the c-th DL CC. If a transmission mode for supporting singletransmission block (TB) transmission is configured in the c-th DL CC orif the spatial bundling is applied to the c-th DL CC, O_(c) ^(ACK) maybe identical to B_(c) ^(DL) as denoted by O_(c) ^(ACK)=B_(c) ^(DL). Incontrast, if a transmission mode for supporting transmission of multipletransmission blocks (e.g., two TBs) is configured in the c-th DL CC orif no spatial bundling is applied to the c-th DL CC, O_(c) ^(ACK) may beidentical to 2B_(c) ^(DL) as denoted by O_(c) ^(ACK)=2B_(c) ^(DL). B_(c)^(DL) is the number (i.e., maxPDCCHperCC) of DL subframes requiringACK/NACK feedback in the c-th DL CC. If HARQ-ACK is transmitted throughPUSCH w/ PDCCH′, maxPDCCHperCC may be indicated by the value of a UL-DAIfield. In accordance with this example, when deciding the‘maxPDCCHperCC’ value, the BS may further consider ‘PDSCH w/o PDCCH(e.g., SPS PDSCH)’ (that is, maxPDCCHperCC=3). In contrast, if HARQ-ACKis transmitted through a PUCCH or PUSCH w/o PDCCH, maxPDCCHperCC isdenoted by M (i.e., mxPDCCHperCC=M).

If a transmission mode for supporting transmission of a singletransmission block is established in the c-th DL CC, or if spatialbundling is applied to the c-th DL CC, the position of each ACK/NACK inper-CC HARQ-ACK payload is given as o_(c,DAI(k)-1) ^(ACK). DAI(k)indicates a DL DAI value of the PDCCH detected at the DL subframe (n−k).In contrast, if a transmission mode for supporting transmission ofmultiple transmission blocks (e.g., two transmission blocks) isconfigured in the c-th DL CC and no spatial bundling is applied to thec-th DL CC, the position of each ACK/NACK in per-CC HARQ-ACK payload isdenoted by o_(c,2DAI(k)-2) ^(ACK) and o_(c,2DAI(k)-1) ^(ACK).o_(c,2DAI(k)-2) ^(ACK) is a HARQ-ACK for the codeword 0, ando_(c,2DAI(k)-1) ^(ACK) is a HARQ-ACK for the codeword 1.

On the other hand, according to Option C, if SPS PDSCH is present asshown in the drawing, the HARQ-ACK position for SPS PDSCH may be locatedat HARQ-ACK payload

o_(c, O_(c)^(ACK) − 1)^(ACK)

of the corresponding CC. SPS PDSCH may be limited to a DL CC having thelowest CC index as shown in the drawing. In addition, a CC including SPSPDSCH may be limited to a DL PCC having the lowest CC index. Ifnecessary, the lowest CC index may also be assigned to a DL PCC.

Thereafter, the UE allows HARQ-ACK payload (i.e., HARQ-ACK part for eachCC) for multiple CCs to be sequentially concatenated with each otheraccording to the cell index. Preferably, the HARQ-ACK payload may beconcatenated with each other in ascending numerical order of cell index.The entire HARQ-ACK payload configured by concatenation can betransmitted through a PUCCH or PUSCH upon completion of signalprocessing (e.g., channel coding, modulation, scrambling, etc.).

Embodiment 5

Embodiment 5 proposes a method for determining the number of SPSACK/NACK bits for ACK/NACK transmission. In case of SPS scheduling, ifSPS is activated through PDCCH, a PDSCH is transmitted without a PDCCHat intervals of a predetermined time promised between the BS and the UE.Accordingly, although a PDCCH is not present, the UE can recognizewhether one or more TBs are to be transmitted through the correspondingPDSCH. Thus, if a CC for SPS PDSCH transmission is configured in apredetermined mode in such a manner that multiple TBs can be transmittedover a single PDSCH, it is necessary to obtain the number of ACK/NACKbits per PDSCH based on a maximum number of TBs capable of beingtransmitted according to a transmission mode for each CC, such that itcan properly cope with the absence of PDCCH under a dynamic PDSCH (i.e.,a PDSCH with a corresponding PDCCH) but not SPS PDSCH. However, in thecase of the SPS PDSCH, it may be possible to determine the number ofACK/NACK bits per PDSCH based on the number of TBs allocated during SPSactivation.

For example, it is assumed that SPS PDSCH is configured to schedule onlyone TB irrespective of a transmission mode, and a CC for SPS PDSCHtransmission is configured to a transmission mode capable of supportingtransmission of a maximum of 2 TBs. In this case, for dynamic PDSCH, theUE must reserve 2 ACK/NACK bits even though only one TB is scheduled. Incontrast, for SPS PDSCH, the UE must reserve only one ACK/NACK bit.Therefore, Embodiment 5 can prevent unnecessary ACK/NACK bits from beingallocated to the SPS PDSCH.

FIG. 31 exemplarily shows the ACK/NACK transmission process according tothe embodiment of the present invention. Option A, Option B, and OptionC of FIG. 31 show examples for coupling adaptive ACK/NACK transmissionto Option A, Option B, and Option C of FIG. 29, respectively. Option A,Option B, and Option C exemplarily show adaptive ACK/NACK transmissionmethods under ‘maxPDCCHperCC=2’, and assume that the ‘maxPDCCHperCC’value is determined in consideration of SPS PDSCH. Therefore, the numberof DL subframes, that need ACK/NACK feedback at Option A, Option B, andOption C, is 2. Option D may indicate non-adaptive ACK/NACKtransmission. The position of each ACK/NACK bit within ACK/NACK payloadmay be sequentially determined according to the CC index and thesubframe order. In addition, it is assumed that CC #1 and CC #3 areconfigured with a transmission mode (TM) for supporting transmission oftwo TBs, and spatial bundling is not applied. It is assumed that CC #2and CC #3 are configured with a transmission mode for supportingtransmission of only TB. In addition, it is assumed that SPS PDSCHsupports transmission of only one TB.

Referring to FIG. 31, in case of Option A, Option B, and Option C, theUE generates ACK/NACK bits for two DL subframes per CC. In case ofOption D, the UE generates ACK/NACK bits for two DL subframes per CC.

In association with dynamic PDSCH of CC #1 and CC #3, the UE alwaysallocates 2-bit ACK/NACK information to one PDSCH (or one DL subframe)according to a transmission mode, irrespective of the number of actuallyscheduled TBs. If spatial bundling is applied to CC #1 and CC #3, the UEalways allocates 2-bit ACK/NACK information to one PDSCH (or one DLsubframe) in association with dynamic PDSCH of CC #1 and CC #3. Inaddition, in association with dynamic PDSCH of CC #2 and CC #4, the UEalways allocates 1-bit ACK/NACK information to one PDSCH (or one DLsubframe) for only one TB, irrespective of the number of actuallyscheduled TBs.

In contrast, in association with SPS PDSCH, the UE allocates ACK/NACKbit (for example, one bit) according to the number of TBs actuallyscheduled to SPS PDSCH, irrespective of the number of TBs capable ofbeing maximally scheduled according to a transmission mode of CC #1. Inother words, according to this example of the present invention, SPSPDSCH A/N is always set to 1 bit irrespective of a transmission mode ofa CC through which SPS PDSCH is transmitted.

Provided that a maximum number of TBs capable of being transmitted in asingle DL subframe per CC is set to 1 or 2, the number of HARQ-ACK bitscan be determined as follows.

1) When calculating ‘maxPDCCHperCC’ using SPS PDSCH, the followingrelationship is achieved. Equation 9 shows that a CC for SPS PDSCHtransmission is configured with a transmission mode capable ofsupporting transmission of a maximum of one TB. Equation 10 shows that aCC for SPS PDSCH transmission is configured with a transmission modecapable of supporting transmission of a maximum of 2 TBs.

$\begin{matrix}{O_{{HARQ} - {ACK}} = {{\max \; {{PDCCHperCC} \cdot {\sum\limits_{c = 0}^{C - 1}\; {{TB}_{\max}(c)}}}} = {\max \; {{PDCCHperCC} \cdot \left( {C + C_{2}} \right)}}}} & \left\lbrack {{Equation}\mspace{14mu} 9} \right\rbrack \\{O_{{HARQ} - {ACK}} = {{{\max \; {{PDCCHperCC} \cdot {\sum\limits_{c = 0}^{C - 1}\; {{TB}_{\max}(c)}}}} - 1} = {{\max \; {{PDCCHperCC} \cdot \left( {C + C_{2}} \right)}} - 1}}} & \left\lbrack {{Equation}\mspace{14mu} 10} \right\rbrack\end{matrix}$

2) If PDSCH is not used to calculate ‘maxPDCCHperCC’, the followingequation 11 is achieved.

$\begin{matrix}{O_{{HARQ} - {ACK}} = {{{\max \; {{PDCCHperCC} \cdot {\sum\limits_{c = 0}^{C - 1}\; {{TB}_{\max}(c)}}}} + 1} = {{\max \; {{PDCCHperCC} \cdot \left( {C + C_{2}} \right)}} + 1}}} & \left\lbrack {{Equation}\mspace{14mu} 11} \right\rbrack\end{matrix}$

In Equation 11, if ‘maxPDCCHperCC’ is set to M (maxPDCCHperCC=M, where Mis the number of DL subframes corresponding to one UL subframe), thefollowing exception may be applied to this example. Equation 12 showsthat a CC for SPS PDSCH transmission is configured with a transmissionmode capable of supporting a maximum of one TB. Equation 13 shows that aCC for SPS PDSCH transmission is configured with a transmission modecapable of supporting transmission of a maximum of 2 TBs.

$\begin{matrix}{O_{{HARQ} - {ACK}} = {{\max \; {{PDCCHperCC} \cdot {\sum\limits_{c = 0}^{C - 1}\; {{TB}_{\max}(c)}}}} = {\max \; {{PDCCHperCC} \cdot {\left( {C + C_{2}} \right).}}}}} & \left\lbrack {{Equation}\mspace{14mu} 12} \right\rbrack \\{O_{{HARQ} - {ACK}} = {{{\max \; {{PDCCHperCC} \cdot {\sum\limits_{c = 0}^{C - 1}\; {{TB}_{\max}(c)}}}} - 1} = {{\max \; {{PDCCHperCC} \cdot \left( {C + C_{2}} \right)}} - 1}}} & \left\lbrack {{Equation}\mspace{14mu} 13} \right\rbrack\end{matrix}$

In accordance with the adaptive ACK/NACK transmission scheme, in case ofSPS PDSCH, the number of ACK/NACK bits can be allocated according to thenumber of scheduled TBs. On the other hand, the non-adaptive ACK/NACKtransmission scheme can allocate the number of ACK/NACK bits accordingto a maximum number of TBs capable of being transmitted according to atransmission mode, irrespective of SPS PDSCH. The non-adaptive ACK/NACKtransmission scheme may be preferable to the adaptive ACK/NACKtransmission scheme in that the non-adaptive ACK/NACK transmissionscheme can always use the CC transmission mode and a fixed number ofACK/NACK bits according to the number of DL subframes corresponding toone UL subframe.

In more detail, the following combinations may be utilized in thepresent invention.

-   -   In the first combination, if ACK/NACK is transmitted using a        PUCCH format, the non-adaptive ACK/NACK transmission scheme may        be used (regardless of SPS PDSCH), and the number of ACK/NACK        bits may be allocated according to a maximum number of TBs        capable of being scheduled according to the transmission mode.    -   In the second combination, if ACK/NACK is piggybacked and        transmitted to a PUSCH, the adaptive ACK/NACK transmission        scheme can be used. In addition, in the case of dynamic PDSCH,        the number of ACK/NACK bits can be allocated according to a        maximum number of TBs capable of being scheduled according to        the transmission mode. In contrast, in the case of SPS PDSCH, a        method for allocating the number of ACK/NACK bits according to        the number of scheduled TBs can be applied to the present        invention. If a maximum number of TBs capable of being        transmitted to SPS PDSCH is set to 1 irrespective of the        transmission mode, ACK/NACK information for SPS PDSCH may always        be fixed to one bit.

Embodiment 6

Embodiment 6 proposes the signaling method for selecting ACK/NACKtransmission resources. In the legacy LTE, only a specific format(referred to as Format 1) capable of transmitting ACK/NACK informationfor one PDSCH exists. In addition, in the case of the presence of PDCCH,the UE utilizes PUCCH resources interworking with a CCE through which aPDCCH is transmitted. In the case of SPS, the UE utilizes PUCCHresources that have been allocated from the BS. In contrast, as can beseen from FIGS. 10 and 11, LTE-A proposes multiple ACK/NACK formats(referred to as ‘FormatM’) capable of transmitting multiple ACK/NACKsignals for multiple PDSCHs. Resources for FormatM can be explicitlyallocated to the UE. FormatM must occupy much more physical resourcesthan the legacy Format 1, such that FormatM is far from efficient interms of resource utilization. Therefore, provided that only one PDSCHis actually scheduled although multiple CCs are configured, the legacyFormat 1 may be more preferable than FormatM in terms of resourceutilization.

Therefore, according to the number of ACK/NACK signals to be actuallytransmitted, a PUCCH format and signaling information for indicatingassociated resource selection may be contained in a PDCCH for PDSCHallocation and a PDCCH for indicating SPS release.

By SPS, provided that a PDSCH is periodically scheduled without using aPDCCH, the number of SPS PDSCHs, a PUCCH format, and a transmissionresource may be selected in the corresponding subframe. The ACK/NACKtransmission operation can be changed as follows according toinformation as to whether additional Format1-transmission resources forPS PDSCH A/N transmission are allocated to the UE.

Option 1: Option 1 indicates that additional PUCCH Format1 resources fortransmitting ACK/NACK to SPS PDSCH are not allocated

If only one PDSCH is scheduled to the UE, signaling informationindicating transmission format/resource information is contained in aPDCCH as described above, and ACK/NACK information can be transmittedusing Format 1 as described above. However, if only SPS PDSCH isscheduled, a PDCCH may not exist so that it may be impossible toindicate format/resource selection. In this case, it is impossible toutilize PUCCH resources interworking with a CCE via which a PDCCH istransmitted, such that ACK/NACK information cannot be transmitted usingFormat 1. As a result, assuming that the UE does not detect a PDCCHcausing a UL ACK/NACK and at the same time SPS PDSCH is scheduled,ACK/NACK for SPS PDSCH can be transmitted through PUCCH resourcesallocated to FormatM. However, it should be noted that, under thecondition that a PUSCH is scheduled to a subframe for ACK/NACKtransmission, ACK/NACK can be piggybacked to a PUSCH.

Option 2: Option 2 indicates that additional PUCCH Format1 resources fortransmitting ACK/NACK to SPS PDSCH are allocated

The ACK/NACK transmission process for Option 2 will hereinafter bedescribed with reference to FIG. 32.

Referring to FIG. 32, since a PDCCH may not exist when only SPS PDSCH isscheduled, it may be impossible to indicate PUCCH format/resourceselection. That is, assuming that the UE may not detect any PDCCHcausing a UL ACK/NACK and at the same time SPS PDSCH is scheduled, theUE may transmit ACK/NACK information according to Format 1 throughresources allocated for SPS, without receiving PDCCH indicationinformation. However, it should be noted that ACK/NACK information canbe piggybacked to a PUSCH on the condition that a PUSCH is scheduled toa subframe for ACK/NACK transmission.

FIG. 33 is a block diagram illustrating a base station (BS) and a userequipment (UE) applicable to the embodiments of the present invention.If a relay is contained in a wireless communication system,communication in a backhaul link is achieved between a BS and a relay,and communication in an access link is achieved between a relay and aUE. Therefore, a BS or UE shown in FIG. 33 may be replaced with a relayas necessary.

Referring to FIG. 33, the wireless communication system includes a basestation (BS) 110 (also denoted by ‘BS’) and a UE 120. The BS 110includes a processor 112, a memory 114, and a radio frequency (RF) unit116. The processor 112 may be constructed to implement the proceduresand/or methods disclosed in the embodiments of the present invention.The memory 114 may be connected to a processor 112, and store variousinformation related to operations of the processor 112. The RF unit 116is connected to the processor 112, and transmits and/or receives RFsignals. The UE 120 includes a processor 122, a memory 124, and an RFunit 126. The processor 122 may be constructed to implement theprocedures and/or methods disclosed in the embodiments of the presentinvention. The memory 124 may be connected to a processor 122, and storevarious information related to operations of the processor 122. The RFunit 126 is connected to the processor 122, and transmits and/orreceives RF signals. The BS 110 and/or the UE 120 may include a singleantenna or multiple antennas.

The aforementioned embodiments are achieved by combination of structuralelements and features of the present invention in a predeterminedfashion. Each of the structural elements or features should beconsidered selectively unless specified otherwise. Each of thestructural elements or features may be carried out without beingcombined with other structural elements or features. Also, somestructural elements and/or features may be combined with one another toconstitute the embodiments of the present invention. The order ofoperations described in the embodiments of the present invention may bechanged. Some structural elements or features of one embodiment may beincluded in another embodiment, or may be replaced with correspondingstructural elements or features of another embodiment. Moreover, it willbe apparent that some claims referring to specific claims may becombined with other claims referring to the other claims other than thespecific claims to constitute the embodiment or add new claims by meansof amendment after the application is filed.

The embodiments of the present invention have been described based ondata transmission and reception between a BS (or eNB) and a UE. Aspecific operation which has been described as being performed by the BSmay be performed by an upper node of the BS as the case may be. In otherwords, it will be apparent that various operations performed forcommunication with the UE in the network which includes a plurality ofnetwork nodes along with the BS can be performed by the BS or networknodes other than the BS. The BS may be replaced with terms such as fixedstation, Node B, eNode B (eNB), and access point. Also, the term UE maybe replaced with terms such as mobile station (MS) and mobile subscriberstation (MSS).

The embodiments according to the present invention can be implemented byvarious means, for example, hardware, firmware, software, orcombinations thereof. If the embodiment according to the presentinvention is implemented by hardware, the embodiment of the presentinvention can be implemented by one or more application specificintegrated circuits (ASICs), digital signal processors (DSPs), digitalsignal processing devices (DSPDs), programmable logic devices (PLDs),field programmable gate arrays (FPGAs), processors, controllers,microcontrollers, microprocessors, etc.

If the embodiment according to the present invention is implemented byfirmware or software, the embodiment of the present invention may beimplemented by a module, a procedure, or a function, which performsfunctions or operations as described above. Software code may be storedin a memory unit and then may be driven by a processor. The memory unitmay be located inside or outside the processor to transmit and receivedata to and from the processor through various well known means.

It will be apparent to those skilled in the art that the presentinvention can be embodied in other specific forms without departing fromthe spirit and essential characteristics of the invention. Thus, theabove embodiments are to be considered in all respects as illustrativeand not restrictive. The scope of the invention should be determined byreasonable interpretation of the appended claims and all change whichcomes within the equivalent scope of the invention are included in thescope of the invention.

Exemplary embodiments of the present invention can be applied towireless communication systems such as a UE, a relay, and a base station(BS).

What is claimed is:
 1. A method of receiving uplink control information at a communication apparatus in a wireless communication system configured for Time Division Duplex (TDD) operations and having a plurality of cells, the method comprising: transmitting a first set of at least one of one or more Physical Downlink Control Channel (PDCCH) signals and one or more Physical Downlink Shared Channel (PDSCH) signals within M downlink subframes where M≧1; transmitting a second set of at least one of one or more PDCCH signals and one or more PDSCH signals within N downlink subframes where N≧1; and receiving acknowledgment information on an uplink subframe, the acknowledgment information including first acknowledgment information corresponding to the first set and second acknowledgment information corresponding to the second set, wherein, when a PDSCH signal without a corresponding PDCCH signal is present among the first set, third acknowledgment information in response to the PDSCH signal is placed at an end of the first acknowledgment information corresponding to the first set and is not placed at an end of the acknowledgment information.
 2. The method of claim 1, wherein the third acknowledgment information in response to the PDSCH signal is placed at the end of the first acknowledgment information corresponding to the first set regardless of location of the PDSCH signal without the corresponding PDCCH signal within the first set.
 3. The method of claim 1, wherein the first set and the second set are transmitted on different cells.
 4. The method of claim 1, wherein the first set is transmitted on a Primary Cell (PCell).
 5. The method of claim 1, wherein the uplink subframe is an uplink subframe of a Physical Uplink Shared Channel (PUSCH).
 6. The method of claim 5, wherein a payload size of the acknowledgment information is determined using a Downlink Assignment Index (DAI) value of a PDCCH for PUSCH scheduling.
 7. The method of claim 6, wherein the DAI value indicates a value related with a per-cell acknowledgment information payload size.
 8. The method of claim 1, wherein if the uplink subframe is an uplink subframe of a Physical Uplink Control Channel (PUCCH), a payload size of a per-cell acknowledgment information is determined using a number of downlink subframes corresponding to the uplink subframe.
 9. The method of claim 1, wherein the first acknowledgment information and the second acknowledgment information are concatenated in increasing order of cell index.
 10. The method of claim 1, wherein the M downlink subframes are subframe n−k (kεK), the uplink subframe is subframe n, and the K: {k₀, k₁, . . . , k_(M-1)} is defined in a table below: UL-DL Subframe n Configuration 2 3 4 5 6 7 0 6 — 4 — — 6 1 7, 6 4 — — — 7, 6 2 8, 7, 4, 6 — — — — 8, 7, 4, 6 3 7, 6, 11 6, 5 5, — — — 4 4 12, 8, 7, 11 6, 5, 4, — — — — 7 5 13, 12, 9, 8, 7, 5, 4, — — — — — 11, 6 6 7 7 5 — — 7


11. A communication apparatus configured to receive uplink control information in a wireless communication system configured for Time Division Duplex (TDD) operations and having a plurality of cells, the communication apparatus comprising: a Radio Frequency (RF) unit; and a processor configured to: transmit a first set of at least one of one or more Physical Downlink Control Channel (PDCCH) signals and one or more Physical Downlink Shared Channel (PDSCH) signals within M downlink subframes where M≧1, transmit a second set of at least one of one or more PDCCH signals and one or more PDSCH signals within N downlink subframes where N≧1, and receive acknowledgment information on an uplink subframe, the acknowledgment information including first acknowledgment information corresponding to the first set and second acknowledgment information corresponding to the second set, wherein, when a PDSCH signal without a corresponding PDCCH signal is present among the first set, third acknowledgment information in response to the PDSCH signal is placed at an end of the first acknowledgment information corresponding to the first set and is not placed at an end of the acknowledgment information.
 12. The communication apparatus of claim 11, wherein the third acknowledgment information in response to the PDSCH signal is placed at the end of the first acknowledgment information corresponding to the first set regardless of location of the PDSCH signal without the corresponding PDCCH signal within the first set.
 13. The communication apparatus of claim 11, wherein the first set and the second set are transmitted on different cells.
 14. The communication apparatus of claim 11, wherein the first set is transmitted on a Primary Cell (PCell).
 15. The communication apparatus of claim 11, wherein the uplink subframe is an uplink subframe of a Physical Uplink Shared Channel (PUSCH).
 16. The communication apparatus of claim 15, wherein a payload size of the acknowledgment information is determined using a Downlink Assignment Index (DAI) value of a PDCCH for PUSCH scheduling.
 17. The communication apparatus of claim 16, wherein the DAI value indicates a value related with a per-cell acknowledgment information payload size.
 18. The communication apparatus of claim 11, if the uplink subframe is an uplink subframe of a Physical Uplink Control Channel (PUCCH), a payload size of the acknowledgment information is determined using a number of downlink subframes corresponding to the uplink subframe.
 19. The communication apparatus of claim 11, wherein the first acknowledgment information and the second acknowledgment information are concatenated in increasing order of cell index.
 20. The communication apparatus of claim 11, wherein the M downlink subframes are subframe n−k (kεK), the uplink subframe is subframe n, and the K: {k₀, k₁, . . . , k_(M-1)} is defined in a table below: UL-DL Subframe n Configuration 2 3 4 5 6 7 0 6 — 4 — — 6 1 7, 6 4 — — — 7, 6 2 8, 7, 4, 6 — — — — 8, 7, 4, 6 3 7, 6, 11 6, 5 5, 4 — — — 4 12, 8, 7, 11 6, 5, 4, — — — — 7 5 13, 12, 9, 8, 7, 5, 4, — — — — — 11, 6 6 7 7 5 — — 7 